OF  THE 

UNIVERSITY 

OF 


EDUCATION  EIBH; 


63$ 


ELEMENTARY    LESSONS 


ZOOLOGY 


A   GUIDE   IN   STUDYING   ANIMAL   LIFE   AND 

STKUCTUKE   IN    FIELD   AND 

LABORATORY 


BY 


JAMES   G.    NEEDHAM,   M.S. 

INSTRUCTOR  IN  ZOOLOGY,  KNOX  COLLEGE,  GALESBURG,  ILL. 


<*>:*I< 


NEW  YORK  ...  CINCINNATI  •-..  CHICAGO 

AMERICAN    BOOK    COMPANY 


"  The  invariable  adaptation  of  an  animal  to  the  life  it  leads  is  one  of 
nature's  most  instructive  lessons,  and  can  be  discovered  and  appreciated 
by  every  pupil,  but  never  through  oral  teaching  or  from  reading  of 
books.  Setter  a  child  should  learn  to  handle  one  animal,  to  see  and 
know  its  structure  and  how  it  lives  and  moves,  than  to  go  through  the 
whole  animal  kingdom  with  the  best  text-book  under  the  best  teacher, 
aided  by  the  best  charts  ever  made.  The  former  would  have  learned 
what  real  knowledge  is  and  how  to  get  it,  while  the  latter  would  have 

simply  learned  how  to  pass  at  his  school  examination. " 

ALPHEUS  HYATT. 

"  Therefore  I  would,  in  the  name  of  education,  urge  students  to 
begin  naturally  with  what  interests  them,  with  the  near  at  hand,  with 
the  practically  important.  A  circuitous  course  of  study,  followed  with 
natural  eagerness,  will  lead  to  better  results  than  the  most  logical  of 
programs,  if  that  take  no  root  in  the  life  of  the  student." 

J.  ABTHUR  THOMSON,  in  "  The  Study  of  Animal  Life,"  p.  361. 


EDUCATION  MBB7 

COPYRIGHT,  1895,  1896,  BY 
AMERICAN  BOOK  COMPANY. 


NEED.  ZOOLOGY. 

E-P  8 


PREFACE. 


THIS  book  is  intended  for  that  increasing  class  of  moderately 
equipped  schools  in  which  it  is  desired  to  make  a  beginning  in  the 
study  of  zoology  after  the  scientific  method.  Its  aim  is  to  put  the 
student  in  the  way  of  acquiring  for  himself  a  knowledge  of  animal 
life  and  structure.  It  is  not  intended  to  supersede  the  teacher,  but 
rather  to  relieve  him  from  doing  that  part  of  the  work  for  the  stu- 
dent which  the  student  should  do  for  himself,  and  to  give  the  teacher 
a  wider  opportunity.  It  is  written  in  the  firm  belief  that  the  student 
will  receive  that  benefit  which  belongs  peculiarly  to  this  study  in  just 
so  far  as  he  comes  into  touch  with  nature  through  actual  contact  with 
facts. 

The  plan  presented  has  been  adopted  after  due  deliberation  and 
repeated  trial.  In  the  belief  that  the  simplest  animal  structures  are 
best  for  illustrating  the  fundamental  ideas  of  zoology,  as  well  as 
being  easiest  understood,  four  simple  types  are  introduced  first. 
These  are  for  microscopic  study,  from  material  to  be  provided  by  the 
teacher,  and  prepared  by  him  for  examination.  From  the  study  of 
these  the  student  may  learn  the  purport  of  the  terms  cell,  protoplasm, 
tissue,  organ,  differentiation,  sexuality,  etc.  With  these  fundamental 
ideas  mastered,  he  is  prepared  to  study  intelligently  any  of  the  higher 
animals.  The  novelty  of  the  introductory  microscopic  work  will  be 
a  sufficient  guaranty  of  interest  in  it,  and  the  succeeding  work  is  out- 
lined in  accordance  with  the  tastes  and  in  avoidance  of  the  prejudices 
of  the  beginner.  Insects  are  taken  up  next  in  order,  and  the  most 
attractive  insects  are  studied  first. 

This  is  a  deliberate  but  not  a  purposeless  violation  of  the  logical 
order.  Systematic  zoology  may  well  be  neglected,  so  long  as  the 
student  is  ignorant  of  the  material  to  be  classified.  To  start  the 
beginner  where  the  specialist  leaves  off  is  an  error  too  often  repeated 
in  the  teaching  of  this  as  of  other  sciences.  Wherever,  in  the 
arrangement  of  the  subject-matter  of  this  book,  the  choice  has  seemed 

M577O41 


4  PREFACE. 

to  lie  between  being  logical  and  being  serviceable,  the  author  has 
preferred  that  the  arrangement  should  be  serviceable. 

The  study  of  animals  alive,  and  in  their  biological  relations  to  their 
environment,  is  made  a  prominent  feature.  It  is  not  morphology,  or 
physiology,  or  natural  history  alone,  that  constitutes  a  proper  ele- 
mentary zoological  course,  but  a  comprehensive  study  of  animals,  that 
develops  these  sciences  in  their  proper  relations,  and  gives  the  ele- 
mentary student  a  general  view  of  the  whole  field,  —  a  correct 
"  zoological  perspective."  Morphology  may,  perhaps,  like  chemistry, 
be  learned  in  the  laboratory  alone,  but  zoology  may  not.  It  has  been 
a  popular  delusion  that  a  term  of  dissections  constitutes  a  proper  ele- 
mentary course.  Such  a  course  was  an  improvement  on  former 
methods :  the  study  of  dead  animals  is  infinitely  better  than  no  con- 
tact with  animals  at  all.  But  to  study  animals  with  nature  and  life 
left  out  is  to  omit  a  phase  of  the  subject  of  deepest  scientific  interest, 
of  highest  educational  importance,  and  of  greatest  pedagogical  utility. 

This  book  is  written  primarily  for  use  in  the  interior  :  hence 
forms  of  life  obtainable  only  at  the  seashore  receive  less  attention 
than  those  found  inland.  The  study  of  animal  life  is  best  begun 
with  forms  nearest  at  hand.  The  custom  of  sending  to  the  seashore 
for  specimens  with  which  to  begin  the  study,  and  neglecting  a  wealth 
of  material  at  home,  does  not  deserve  to  be  encouraged.  At  the  sug- 
gestion of  many  teachers  who  live  where  fresh  marine  material  is 
available,  a  study  of  the  starfish  is  inserted  as  the  last  chapter  in  the 
book.  Believing  that  it  will  be  used  in  some  cases  where  material  to 
illustrate  it  is  insufficient,  it  contains  fewer  interrogation  points,  and 
more  of  explicit  statement,  than  preceding  chapters.  A  few  diagrams 
of  structures  are  inserted  for  the  same  reason. 

All  the  work  outlined  in  the  following  pages  has  been  tested  in  the 
classroom,  and  has  been  repeatedly  performed  by  the  author  while 
drawing  up  these  lessons ;  and  it  is  hbped  by  him  that  they  may  prove 
reasonably  free  from  ambiguity  and  error.  Xo  animal  is  studied 
exhaustively :  each  one  lends  itself  to  some  special  purposes  of  illus- 
tration, and  to  such  ends  only  is  it  used.  Care  has  been  taken  to 
introduce  no  work  beyond  the  capacity  of  the  beginner.  The  illustra- 
tions given  are  intended  to  guide  the  student  in  finding  and  identify- 
ing for  himself  the  animals  recommended  in  the  text  for  study.  Few 
drawings  are  given  of  things  which  the  student  may  reasonably  be 
expected  to  draw  for  himself.  If  such  are  wanted,  the  reference 
books  recommended  are  filled  with  them,  and  may  be  consulted  with 
profit. 

In  the  material  presented  herein  the  author  can  lay  no  claim  to 


PREFACE.  5 

originality :  he  only  wishes  to  be  given  credit  for  an  honest  effort  at 
selecting,  from  the  most  available  materials  offered,  that  best  calcu- 
lated for  introducing  the  beginner  to  the  ideas  and  principles  of 
zoological  science.  lie  respectfully  invites  the  correspondence  of 
teachers  who  find  difficulty  in  using  the  book. 

Finally,  the  author  would  gratefully  acknowledge  the  assistance  of 
many  friends  and  teachers  and  of  books  which  were  teachers.  He 
would  speak  of  the  cut  on  p.  212,  which  was  kindly  loaned  by 
Professor  Forbes  of  the  Illinois  State  Laboratory  of  Natural  History : 
and  he  would  especially  remember  the  assistance  of  Dr.  E.  A.  An- 
drews of  Johns  Hopkins  University,  who  read  the  manuscript  of  the 
text;  of  Professor  J.  H.  Comstock  of  Cornell  University,  who  read 
the  proof  sheets  of  the  pages  relating  to  insects ;  of  Professor  E.  A. 
Birge  of  the  University  of  Wisconsin,  who  read  the  proof  sheets  of 
the  pages  relating  to  crustaceans,  mollusks,  and  vertebrates ;  of  Mr. 
Edward  Potts  of  Philadelphia,  who  read  the  manuscript  of  the  pages 
relating  to  the  fresh- water  sponge ;  of  his  honored  friend  and  teacher, 
Professor  Hurd  of  Knox  College,  who  revised  the  etymological  list  of 
technical  terms;  and,  last  but  not  least,  of  his  wife,  Anna  Taylor 
Needham,  who  made  pen  drawings  for  most  of  the  illustrations. 

J.  G.  N. 


CONTENTS. 


PAGE 

INTRODUCTION        9 

PROTOZOANS 12 

The  Amoeba 12 

The  Slipper  Animalcule 18 

CCELENTERATES , 22 

The  Fresh-water  Sponge 22 

The  Hydra 26 

INSECTS 34 

Hexapod  Insects 36 

The  Butterfly 36 

The  Dragon  Fly 42 

The  Grasshopper 48 

The  Squash  Bug 67 

The  Two-year  Cicada 69 

The  Back-Swimmer 61 

The  Bumblebee 63 ' 

The  Mud  Wasp 70 

The  Paper  Wasp 72 

The  Honeybee 73 

The  Black  Blister  Beetle 74 

The  Bluebottle  Fly 80 

The  Bee  Killer 84 

The  Cabbage  Butterfly 86 

The  Life  Process  in  Insects 93 

A  Review  Exercise 99 

A  Lesson  in  Classification 101 

Arachnid  Insects    .     .    , 105 

The  Spider 105 


8  CONTENTS. 

PAGE 

Myriapod  Insects 109 

The  Chilopod  or  Centiped 109 

CRUSTACEANS Ill 

The  Crawfish Ill 

TheAsellus 125 

The  Cyclops 126 

Further  Classification 127 

WORMS 130 

The  Earthworm 130 

MOLLUSKS 140 

The  River  Mussel 140 

The  Pond  Snail 154 

VERTEBRATES 161 

The  Catfish 161 

The  Frog 178 

The  Turtle 198 

The  Snake ....  208 

The  English  Sparrow 211 

The  Rabbit 237 

The  Life  Process  in  Vertebrates 260 

ECHINODERMS 266 

The  Starfish 266 

APPENDIX 275 

Prerequisites 275 

Reagents 276 

Directions  for  the  Preparation  of  Material  for  Study     ....  278 

Accentuated  List  of  Technical  Terms 288 

Suggestions  to  the  Teacher 302 

INDEX  .                                                                                                           .  305 


INTRODUCTION. 


The  Study  of  Animal  Life  is  begun  when  we  first  learn 
the  names  of  our  household  pets,  and  begin  to  note  the 
differences  between  them.  It  is  continued  so  long  as  our 
eyes  and  ears  are  open  to  observe  the  nature  and  capacities 
of  the  animals  with  which  our  daily  life  brings  us  in  con- 
tact. The  horses  that  draw  our  carriage,  the  dogs  that 
answer  our  call,  the  birds  that  delight  our  ears  with  their 
songs  from  the  tree  tops,  the  insects  that  flit  before  our 
eyes  among  the  flowers  of  the  garden,  —  all  are  continually 
illustrating  phases  of  animal  life,  some  of  which  cannot 
escape  the  notice  of  the  most  casual  observer. 

Every  one  knows  that  animals  must  have  food.  When 
they  are  young,  they  require  food  for  growth ;  and  when 
they  are  grown,  they  require  food  to  furnish  bodily  strength. 
They  require  air  also,  — fresh  air,  containing  oxygen,  for 
the  oxygen  is  the  essential  thing.  A  bird  inclosed  in  an 
air-tight  box  with  plenty  of  food,  or  a  fish  placed  in  a  small 
quantity  of  clean  water,  soon  dies,  because  the  available 
supply  of  oxygen  is  soon  exhausted. 

Every  one  knows  that,  sooner  or  later,  animals  die,  and 
that  they  leave  descendants  to  perpetuate  their  race  upon 
the  earth ;  and  every  one  should  know  that  not  all  their 
young  come  to  maturity,  and  that  the  number  of  their  prog- 
eny is  proportioned  to  the  vicissitudes  to  which  their  life 
is  exposed. 

Every  one  knows  that  animals  move,  that  most  of  them 
move  freely  from  place  to  place,  and  that  those  which  are 

9 


10  INTRODUCTION. 

fixed  in  their  location,  like  the  oyster,  move  freely  some 
parts  of  their  bodies  in  obtaining  their  food. 

Every  one  knows  that  animals  feel,  that  they  respond 
to  stimuli  from  without  and  to  impulses  from  within,  and 
that  the  most  familiar  animals  exhibit  varying  degrees  of 
instinct  and  intelligence. 

These  plain  facts  are  fundamental.  All  the  phenomena 
of  animal  life  may  be  grouped  under  four  heads :  — 

1.  All  those  processes  which  are  concerned  with  feeding 
and  growth,  —  the  taking  of  food,  the  preparation  of  it  for 
the  use  of  the  body,  the  carrying  of  it  in  solution  to  the 
various  parts,  the  building  of  it  into  the  body  structure, 
the  exposure  of  it  to  oxygen  derived  from  the  air,  and  the 
removal  of  useless  portions  and  of  Avaste  materials  from 
the  body  (whether  performed  by  simple  means  or  by  com- 
plex, whether  without  organs  or  by  means  of  many  separate 
organs),  —  all  may  be  called  phenomena  of  Nutrition. 

2.  All  the  phenomena  connected  with  the  reproductive 
process  may  be  called  phenomena  of  Reproduction. 

3.  All  the  phenomena  of  free  and  spontaneous  move- 
ment may  be  called  phenomena  of  Voluntary  Motion. 

4.  All  the  phenomena  of  the  senses  of  instinct  and  of 
intelligence  may  be  called  phenomena  of  Sensation. 

It  will  then  need  to  be  borne  in  mind  that  this  fourfold 
division  is  made  for  convenience ;  that  the  four  groups  of 
phenomena  are  not  entirely  distinct,  but  interrelated  and 
interdependent. 

In  the  beginning  we  must  distinguish  between  that  which 
is  necessary  and  that  which  is  only  accessory  in  animal 
structure.  The  robin  has  a  beak  for  eating,  and  wings  for 
getting  about ;  but  beak  and  wings  are  not  necessary  for 
animal  existence.  Eating  and  moving  are  necessary,  but 
these  might  be  effected  in  other  ways.  The  robin  is  a  bird 
because  of  its  beak  and  wings,  an  animal  only  because  it 
eats  and  moves  at  will. 


INTRODUCTION.  11 

In  studying  each  animal,  if  we  ask,  (1)  What  is  its  food, 
how  obtained  and  how  used  ?  How  does  it  get  oxygen  from 
the  air?  How  does  it  get  rid  of  waste  and  worn-out  mate- 
rial from  its  body?  (2)  How  does  it  reproduce  its  kind? 
How  numerous  are  its  progeny  and  to  what  danger  exposed? 
(3)  How  does  it  move  ?  What  are  its  specially  movable 
parts  ?  (4)  What  powers  of  sense,  of  instinct,  and  of  intel- 
ligence has  it,  and  what  sort  of  a  nervous  system  as  the 
seat  of  these  powers  ?  —  and  if  we  follow  patiently  where 
Nature  leads  until  we  have  found  satisfactory  answers  to 
these  questions, — we  shall  arrive  at  a  better  comprehension 
of  the  animal's  activities,  and  in  the  end  shall  have  learned 
many  lessons  of  perennial  interest  and  profit.  This  four- 
fold division  of  animal  phenomena  will  be  of  service  as  an 
outline  for  our  future  study,  leading  us  to  learn  for  each 
animal  all  we  can  about 

I.   Nutrition,  and  its  subservient  organs. 
II.   Reproduction,  and  the  adaptation  of  the  reproduc- 
tive process  to  varying  conditions  of  life. 

III.  Voluntary  Motion  and  motor  organs. 

IV.  Sensation,  as  manifest  through  a  nervous  system  in 
senses,  instinct,  and  intelligence. 


PROTOZOANS. 

THE    AMCEBA. 

The  Amoeba  is  selected  as  the  first  animal  for  study, 
because  of  its  extreme  simplicity.  In  it  we  are  dealing 
with  animal  life  at  its  lowest  terms. 

It  is  very  small,  usually  less  than  a  hundredth  of  an 
inch  in  diameter,  and  can  be  studied  only  with  the  aid  of 
a  microscope.  Examine  one  that  has  been  taken  up  in  a 
drop  of  water,  mounted  on  a  glass  slip,  covered,  and  placed 
in  the  field  of  a  microscope.1 

First  find  it.  This  will  be  task  enough  for  a  moment 
for  a  beginner,  even  if  the  amoeba  be  in  the  field;  for  it 
presents  so  little  likeness  to  familiar  animals,  that  it  might 
as  readily  be  taken  to  be  anything  else.  It  appears  like  a 
little  drop  of  jelly  spreading  out  on  a  flat  surface,  trans- 
lucent in  its  central  portion,  and  very  transparent  around 
its  border.  Reference  to  the  accompanying  figure  will  aid 
in  recognizing  it.  That  it  is  alive  will  not  be  ascertained 
at  the  first  glance,  but  may  be  learned  from  watching  its 
slowly  changing  outline  for  a  moment  or  two.  After  find- 
ing it,  and  after  learning  by  a  few  trials  how,  by  moving1 
the  glass  slide,  to  bring  it  back  into  the  center  of  the  field 
when  it  moves  out,  and  how  to  keep  it  in  focus  by  turning 
the  adjustment  screws  on  the  microscope,  then  study  its 
general  structure  and  its  movements. 

1  If  the  student  be  working  alone,  he  will  follow  the  directions  given 
to  the  teacher  (see  Appendix,  p.  278)  for  collecting  amcebas,  and  pre- 
paring them  for  examination. 

12 


THE   AMCEBA. 


13 


Observe  :  1.  A  granular,  translucent  central  portion  (the 
endosarc),  with  something  of  the  appearance  of  ground 
glass. 

2.  A  transparent  outer  border  (the  ectosarc),  so  clear  it 
is  liable  to  be  overlooked  the  first  time  an  amoeba  is  seen, 
and  the  endosarc  taken  for  the  whole  animal. 

3.  Irregular,   blunt    projections    (pseudopodia,  or  false 
feet),  which  are  slowly  pushed  out  from  the  body  wall,  or 
drawn  into  it.     Observe  that  in  all  of  these  there  is  the 


AMCEBA  (X  500),  drawn  while  moving  in  the  direction  of  the  arrow: 
nu,  nucleus ;  v,  vacuole ;  ps,  pseudopodia. 

same  clear  border  and  granular  central  portion ;  and  this 
is  true  of  their  appearance  when  they  protrude  vertically, 
as  well  as  when  extended  laterally.  If  we  can  roll  an 
amceba  over,  we  shall  see  the  same  arrangement  of  parts ; 
so  that  we  must  conclude  that  the  ectosarc  forms  a  com- 
plete outer  layer  about  the  whole  animal.  . 

Pseudopodia.  —  Watch  the  formation  of  pseudopodia. 
See  first  a  protrusion  of  the  clear  ectosarc,  then  the  flowing 
of  the  more  fluid  granular  endosarc  out  into  it.  *  Observe 


14  PROTOZOANS. 

that,  while  pseudopodia  are  pushed  out  in  all  directions, 
they  grow  principally  in  one  direction,  and  that  the  direc- 
tion in  which  the  amoeba  is  traveling.  Observe  that  about 
as  fast  as  pseudopodia  are  formed  in  one  direction,  the  body 
follows  them,  all  its  granular  content  flowing  into  their 
bases,  swelling  them,  and  uniting  them. 

Watch  also  the  withdrawal  of  pseudopodia,  first  a  flow- 
ing toward  the  center  of  the  granular  part,  leaving  an 
emptied  projection  of  ectosarc,  which  follows  on  in  the  rear. 

Such  is  amoeba's  primitive  method  of  locomotion.  The 
pseudopodia  which  are  pushed  out  on  one  side  hold  their 
ground ;  and,  when  the  semifluid  body  begins  to  follow, 
they  advance,  and  the  whole  mass  is  seen  setting  forward 
in  an  exceedingly  slow,  flowing  or  gliding  motion. 

If  an  active  amoeba  be  watched  a  short  time,  it  may  be 
seen  to  change  its  direction.  To  do  this  it  does  not  need 
to  turn  around:  it  simply  puts  out  pseudopodia  in  the 
new  direction,  and  follows  them.  It  has  neither  head  nor 
tail.  All  parts  are  alike,  and  one  is  as  well  adapted  as 
another  to  go  first.  It  may  be  seen  to  avoid  large  objects 
with  which  it  comes  in  contact  in  its  course.  If  it  meet  a 
conveniently  small  object,  it  may  sometimes  be  seen  to 
encircle  it  with  pseudopodia,  and  ingulf  it  into  its  soft 
body  mass,  —  swallow  it,  so  to  speak,  —  after  which  the 
object  may  be  seen  within  the  granular  endosarc,  where  it 
is  lodged  as  food  for  digestion.  If  it  prove  indigestible, 
it  is  gotten  rid  of  in  a  correspondingly  simple  way.  The 
body  mass  flows  away  from  it,  and  it  is  left  behind. 

If  the  amoeba  be  irritated  in  any  way,  as  by  touching 
the  cover  glass,  it  immediately  draws  in  its  pseudopodia, 
and  assumes  a  more  or  less  spherical  form.  If  not  injured 
in  any  way,  it  soon  resumes  activity. 

Make  a  series  of  half  a  dozen  outlines  of  an  amoeba, 
drawn  at  intervals  of  a  minute  or  two,  or  less  if  it  be 
moving  actively,  to  show  the  changes  in  form. 


THE   AMCEBA.  15 

Minute  Structures.  —  If  the  currents  in  an  active  amoeba 
have  been  watched  carefully  under  high  power,  certain 
minute  structures  will  have  been  discovered  within  the 
body.  Three  of  these  are  normally  present,  though  not 
always  easily  made  out :  — 

1.  A  nucleus,  a  discoid  or  spherical  body  slightly  more 
transparent  than   the   surrounding  endosarc,  and  usually 
located  toward  the  posterior  end  of  a  moving  amoeba. 

2.  A  contractile  vesicle,  a  round  clear  spot  within  the 
ectosarc.     It  may  sometimes  be  seen  to  contract,  and  dis- 
appear  temporarily,    and   will    then   be   certainly  recog- 
nized. 

3.  Ingested  food  particles.     These  appear  darker  than 
the  surrounding  endosarc ;  or  if  colored  food  particles  have 
been  taken,  microscopic  green  plants,  etc.,  the  color  will 
shine  through.     These  are  of  various  sizes. 

These  structures  may  be  more  readily  made  out  in  a 
specimen  that  is  stained  with  iodine.  Place  a  drop  of 
iodine  solution  on  the  slide  at  one  edge  of  the  cover  glass, 
and  place  a  bit  of  blotting  paper  at  the  opposite  edge. 
The  blotting  paper,  by  its  absorbent  action,  will  draw  the 
iodine  solution  under  the  cover  glass,  where  it  will  pene- 
trate and  stain  and  kill  the  amoeba.  The  nucleus  will  be 
more  brightly  stained  than  the  other  parts. 

Make  an  enlarged  drawing  of  an  amoeba  prepared  in  this 
way,  showing  all  the  points  of  structure  you  have  been 
able  to  see. 

By  mixing  some  very  finely  powdered  carmine  or  indigo 
in  the  drop  of  water  containing  amoebas  before  covering, 
their  feeding  may  sometimes  be  better  observed. 

Occasionally  an  amoeba  may  be  found  dividing  into  two. 
Such  should  be  watched  carefully. 

The  Life  Process.  —  The  jelly-like  living  substance  which 
makes  up  the  body  of  the  amoeba  is  protoplasm.  It  is 


16  PROTOZOANS. 

an  almost  structureless  and  colorless  substance,  in  chemi- 
cal composition  much  like  the  albumen  of  an  egg.  It  is 
the  physical  basis  of  life.  Neither  animal  nor  vegetable 
life  is  known  to  exist  apart  from  it.  It  is  everywhere 
present  in  the  growing  parts  of  animals  and  plants.  It  is 
capable,  as  life's  agent,  of  producing  the  most  complex 
structures.  The  nucleus  within  the  amoeba  is  but  a  bit 
of  the  protoplasm  of  slightly  firmer  consistency  than  the 
rest ;  but  it  is,  perhaps,  the  most  essential  part. 

Simple  as  the  amoeba  is,  and  wanting  in  parts,  it  yet 
leads  an  animal  life,  and  exercises  all  the  essential  animal 
functions. 

I.  Nutrition.  —  That  the  amoeba  takes  food  has  been  seen 
already.  Having  neither  mouth  nor  stomach,  it  ingests  and 
digests  its  food  at  the  most  convenient  point.  Its  proper 
food  consists  of  the  smallest  microscopic  plants.  These, 
when  found  within  the  body  of  a  living  amoeba,  may,  by 
continued  watching,  be  seen  to  dissolve  away  as  they  are 
digested.  The  small  amount  of  mineral  food  and  the 
larger  amount  of  oxygen  necessary  for  the  amoeba  are 
already  in  solution  in  the  water  in  which  it  lives,  and 
need  but  to  be  absorbed.  These  dissolved  foods  penetrate 
freely  to  every  part  of  the  protoplasmic  mass,  and  by  a 
process  called  assimilation  they  are  incorporated  into  it, 
and  become  a  part  of  it.  But  this  process  means  more 
than  the  mere  storing  of  digested  food :  it  means  that  the 
food  is  built  up  into  complex  chemical  compounds,  like 
those  which  are  the  constituents  of  protoplasm,  and  that 
it  then  becomes  a  part  of  the  protoplasm,  like  any  other 
part,  in  all  its  properties.  The  necessary  result  of  this 
process  is  that  the  animal  grows. 

But  this  process  also  makes  possible  the  animal's  activi- 
ties. The  complex  chemical  compounds  formed  in  this 
constructive  process  are  highly  charged  with  potential 
energy  and  are  very  unstable,  like  a  single  tier  of  bricks 


THE   AMCEBA.  17 

that  is  piled  too  high,  or  like  a  train  of  gunpowder  that 
is  ready  to  be  discharged.  As  a  light  touch  will  upset 
the  bricks  and  cause  them  to  fall  with  great  force,  or  as  a 
spark  will  ignite  the  gunpowder  and  cause  a  violent  explo- 
sion, so,  in  a  small  way,  a  slight  stimulus  to  the  amoeba 
will  cause  some  of  these  complex  molecules  in  the  proto- 
plasm to  break  up  into  simpler  ones  with  the  liberation  of 
the  forces  manifested  in  the  animal's  activities. 

The  simple  compounds  (carbonic-acid  gas,  water,  etc.) 
formed  in  this  destructive  process  are  of  no  use  to  the 
amoeba,  and  must  be  removed.  The  name  of  the  process  is 
excretion.  These  waste  products  pass  out  directly  through 
the  body  Avail  into  the  surrounding  water.  It  should  be 
noted  that  there  is  an  important  difference  between  this 
true  process  of  excretion  and  the  mere  egesting  of  an  indi- 
gestible bit  of  carmine :  the  latter  does  not  become  a  part 
of  the  animal's  structure  at  all.  Many  such  particles  are 
ingested  in  the  course  of  feeding.  It  shows  little  choice  in 
the  selection  of  food,  ingulfing  any  object  of  convenient 
size  with  which  it  may  come  in  contact. 

II.  Reproduction. — The  common  method  of  reproduc- 
tion in  amoeba  is  simple  division.    First  the  nucleus  divides 
into  two.     Then  the  body  elongates,  and  the  nuclei  move 
apart  toward  the  ends.     A  furrow  then  appears  across  the 
body,  between  the  nuclei.     This  furrow  deepens  until  it 
entirely  separates  the  body  into  two  pieces,  each  of  which 
is  at  once  an  independent,  perfect  amoeba. 

The  converse  of  this  process  has  been  observed.  Two 
amoebas  have  been  seen  to  fuse  together  into  one.  It  is 
believed  that  this  process  (conjugation)  is  necessary  for 
the  continued  existence  of  amoebas.  It  has  been  proved  to 
be  necessary  in  the  case  of  some  other  microscopic  animals 
which  reproduce  ordinarily  by  dividing. 

III.  Voluntary  Motion. — Protoplasm  is  contractile,  i.e., 
capable  of  extending  in  one  direction  by  shortening   in 

NEED.   ZOOL.  —2 


18  PROTOZOANS. 

another.  But  the  movements  of  amoeba,  simple  as  they 
are,  are  yet  more  than  the  independent  automatic  contrac- 
tions of  protoplasm  ;  for  they  are  controlled  and  coordi- 
nated to  certain  ends,  —  to  reaction  in  response  to  stimuli 
from  without,  to  locomotion  and  to  securing  food  in 
response  to  impulses  from  within. 

IV.  Sensation.  —  These  latter  acts  indicate  spontaneous 
activity,  and  show  that  the  amoeba  possesses  in  a  low 
degree  sensibility,  the  dawning  of  faculties  which  are  the 
highest  endowment  of  animal  life. 

The  Cell.  — The  cell  in  biology  is  a  minute  mass  of  pro- 
toplasm containing  a  nucleus  with  or  without  a  cell  wall. 
The  amoeba  is  a  single  cell  that  has  developed  about  itself 
a  very  delicate  and  pliant  cell  wall. 

The  cell  is  the  unit  of  all  organic  structure.  Every 
plant  and  every  animal  begins  its  existence  as  a  single 
cell.  This  cell  grows  and  divides  repeatedly;  and  the 
cells  thus  formed  remain  together,  and  with  their  products 
compose  the  bodies  of  the  higher  plants  and  animals.  The 
cellular  character  of  the  growing  parts  of  all  animals  may 
be  easily  recognized  under  the  microscope. 

When  the  amoeba  divides,  its  parts  separate.  It  there- 
fore retains  this  simple  condition,  never  becoming  more 
than  a  single  cell. 


THE  SLIPPER  ANIMALCULE. 

(Paramecium.) 

Study  of  Live  Specimens.  —  Examine  a  drop  of  water 
containing  slipper  animalcules.  They  appear  as  minute 
white  specks  rapidly  moving  to  and  fro  through  the  water, 
just  large  enough  to  be  seen  without  a  lens. 

Examine  under  the  microscope  a  drop  that  has  been 
mounted  on  a  slide  in  cotton  fibers,  or,  better,  in  cherry- 


THE   SLIPPER   ANIMALCULE.  19 

gum  solution,  and  covered.1  Use  low  power  at  first,  and 
make  a  general  survey  of  the  contents  of  the  drop.  Sev- 
eral kinds  of  animalcules  may  be  present.  The  slipper 
animalcule  (Paramecium)  may  be  recognized  by  its  elon- 
gated, somewhat  slipper-shaped  form,  and  by  its  rapid  pro- 
gression with  one  end  always  forward. 

Study  its  actions.  Observe  that  paramecium,  unlike 
amoeba,  when  it  reverses  its  direction  of  travel,  turns 
around ;  that  it  has  anterior  and  posterior  ends.  Yet  it 
can  and  does  move  backward  when  cornered,  as  may  be 
seen  when  one  swims  into  a  narrow  space  between  two 
cotton  fibers,  and  has  to  batik  out. 

Find  one  that  may  be  retained  within  the  center  of  the 
field,  and  examine  it,  magnified  300  to  500  diameters. 
Observe :  — 

1.  That  paramecium  has  a  definite,  permanent,  though 
unsym metrical  shape. 

2.  That  its  body  is  a  single  minute  mass,  without  par- 
titions or  divisions ;  i.e.,  that  it  is  a  single  cell. 

3.  That  its  body  mass  is  made  up  of  two  layers,  — 
(#)  An  outer,  transparent  ectosarc. 

(6)   An  inner,  granular,  and  more  fluid  endosarc. 

4.  That  the  whole  body  is  covered  over  with  delicate, 
transparent  processes,  shaped  somewhat  like  eyelashes,  and 
hence  called  cilia.    In  an  active  paramecium,  these  cilia  are 
moved  so  rapidly,  they  may  be  seen  but  dimly,  like  the 
spokes  of  a  rapidly  revolving  wheel.     It  is  by  means  of 
these  cilia  that  the  paramecium  swims.     They  are  used  as 
a  boy's  arms  are  used  in  swimming :  they  are  struck  back- 
ward quickly  and  forcibly,  and  are  drawn  forward  again 
more  slowly.     It  must  be  noted  that  they  are  not  hairs, 
but  only  delicate  projections  from  the  body  wall. 

Observe  also,  focusing  up  and  down  to  bring  into  view 
the  parts  at  different  levels,  — 

1  See  Appendix,  p.  279. 


20 


PKOTOZOANS. 


5.   An  oblique  groove  (peristome)  extending  from  the 
anterior  end  halfway  along  one  side  of  the  animal,  and  so 

twisted  that  its  edges  form  an 
elongated  8-shaped  figure  when 
viewed  from  the  side  (see  cut). 

6.  A  fringe  of  cilia,  longer  and 
stronger  than  those   of  the   body, 
all  around  the  edge  of  this  groove. 
These  set  up  currents  in  the  water, 
which  may  be  seen,  if  there  be  any 
loose  sediment  in  the  water,  set- 
ting to  Ward  the  posterior  end  of 
this  groove. 

7.  A    funnel-shaped    chamber 
(vestibule,  or  mouth)  in  the  poste- 
rior end  of  this  groove.     Toward 
this  the  currents  in  the  water  tend, 
and  into  it  they  drive  the  particles 
they  sweep  along. 

Near  to  this  chamber,  and  in 
the  central  portion  of  the  body,  is 
an  elongated,  often  spindle-shaped 
nucleus,  often  hardly  visible  with- 
out staining. 

In  one  or  two  places  in  the  body 
there  is  a  clear,  round  spot  of  con- 
siderable size  (usually  one  near 
each  end),  which  regularly  ap- 
pears and  quickly  disappears  sev- 
eral times  a  minute.  Each  of  these 
is  a  contractile  vesicle.  If  one  of 
these  be  watched  very  closely,  it 
will  be  seen  to  have  minute,  radi- 
ating tubes  appearing  around  it  when  it  contracts. 

The  remaining  objects  seen  in  the  endosarc  are  food 


PARAMEOIUM  fx300).  The 
water  current  is  driven  in 
the  direction  of  the  large 
arrow  by  the  lashing  ac- 
tion of  the  cilia  of  that  re- 
gion. Food  particles  pass 
down  the  funnel-shaped 
esophagus  (e),  and  col- 
lect in  little  round  pellets 
at  the  bottom.  Then  they 
circulate  about  the  body 
in  the  direction  of  the 
arrows,  and  indigestible 
portions  are  ejected  at  «. 
Two  contractile  vacuoles 
(t>)  are  seen  near  the  ends 
of  the  body,  and  an  elon- 
gate nucleus  (ri)  may  be 
seen  after  staining. 


THE    SLIPPER   ANIMALCULE.  21 

balls  and  minute  fat  globules,  and  various  foreign  bodies 
that  have  been  swept  into  the  mouth  with  food.  The  feed- 
ing habits  of  the  animal  are  best  studied  after  putting 
some  finely  powdered  carmine  or  indigo  into  the  drop  of 
water  with  it.  Bits  of  these  indigestible  substances  will 
be  seen  swept  along  the  groove  by  its  cilia,  through  the 
mouth,  if  they  be  small  enough,  for  this  is  the  only 
entrance  requirement,  and  down  a  sort  of  short  rudimen- 
tary esophagus,  at  the  bottom  of  which  they  collect  into 
a  little  pellet  before  being  ingulfed  by  the  protoplasmic 
mass  of  the  interior.  Then  they  may  be  seen  to  circulate 
slowly  about  the  body,  and,  after  considerable  time,  to 
collect  at  a  point  about  halfway  between  the  mouth  and 
the  posterior  end  of  the  body,  where  they  are  egested 
directly  through  the  body  wall. 

The  Life  Process.  —  This  is  essentially  as  in  amoeba ; 
but  there  are  some  interesting  differences  in  its  details. 

When  any  part  of  an  animal  becomes  so  modified  as  to 
be  better  fitted  for  doing  some  one  thing,  that  part  is  said 
to  be  specialized.  Thus  in  paramecium  the  cilia  are 
specialized  for  locomotion.  One  circlet  of  cilia  —  that 
fringing  the  groove  leading  to  the  mouth  —  is  still  more 
highly  specialized  for  setting  up  currents  in  the  water  as 
a  means  of  capturing  food.  A  mouth  and  short  esophagus 
are  specialized  for  receiving  food,  and  contractile  vesicles 
are  specialized  for  circulating  the  fluids  of  the  body.  Every 
time  a  vesicle  contracts,  it  drives  its  liquid  contents  out  into 
the  surrounding  body  mass.  These  specialized  parts  in  the 
one-celled  paramecium  foreshadow  the  locomotor,  digest- 
ive, and  circulatory  systems  of  the  many-celled  animals. 

Amceba  and  paramecium  are  representatives  of  the  Pro- 
tozoa, a  large  group  of  microscopic  unicellular  animals  of 
wide  distribution. 


CGELENTERATES. 

THE  FRESH-WATER  SPONGE. 

(Myenia  fluviatilis.) 

Study  of  Live  Specimens.  —  Examine  fresh  specimens.1 
Note:  — 

1.  Their  form. 

2.  Their  attachment:  upon  what  kind  of  surfaces  they 

are  found  growing. 

3.  Their  color. 

4.  Their  odor,  pecul- 
iar,   not   unpleasant   in 
life,  but  rapidly  becom- 
ing very  disagreeable  if 
any  specimens  have  died. 
This   rapid    decomposi- 
tion of  the  sponge  flesh 
betrays   its   animal   na- 
ture. 

Examine  the  surface 
of  the    sponge   with   a 

SPICULES  OF  FRESH-WATER  SPONGE  (My-  d  leng  t    find  th        t 

enia  fluviatilis)  :   a,  skeleton  spicules  ;  & 

the  others,  gemmule  spicules  seen  sidewise  oles    (or    exlialent    open- 
at  6  and  d,  endwise  at  c  and  e.  Qut  of 


life,  currents  of  water  are  continually  flowing. 

Examine  it  still  more  closely  to  find   the  minute  but 
multitudinous  pores  (or  inhalent  openings)  which  cover 


1  Directions  for  collecting  are  given  in  Appendix,  p.  279. 
22 


THE   FRESH-WATER   SPONGE.  28 

almost  the  whole  surface,  and  through  which  the  water 
enters  the  sponge. 

The  sponge  flesh  is  called  sarcode.  Press  upon  it,  and 
note  its  consistency. 

Examining  it  again  with  a  lens,  note  that  it  is  bristling 
with  the  points  of  very  minute  spicules,  which  are  arranged 
somewhat  in  lines,  so  as  to  form  a  sort  of  skeleton,  running 
through  and  supporting  the  sarcode.  These  skeleton  spic- 
ules are  about  ^-§  of  an  inch  long. 

The  sarcode  is  permeated  everywhere  by  minute  canals, 
which  convey  the  water,  taken  in  at  the  pores,  to  large 
canals  communicating  with  the  osteoles.  At  certain  places 
in  the  smaller  canals  there  are  enlargements,  which  are 
lined  with  cells  bearing  cilia.  The  water  currents  are 
believed  to  be  due  to  the  lashing  action  of  these  cilia. 

Gemmules.  —  Imbedded  in  the  sponge  flesh,  and  most 
abundant  near  the  base  of  the  sponge,  observe  a  large 
number  of  small,  round,  yellowish  or  brownish  seedlike 
bodies;  about  the  size  of  the  smallest  mustard  seeds.  These 
are  called  gemmules. 

Study  gemmules  which  have  been  cleared  and  mounted 
for  examination.1  Under  low  power  of  microscope,  ob- 
serve the  thick,  yellowish  coat  of  the  gemmule  opening  at 
one  side  by  a  foraminal  aperture  (called,  usually,  simply 
the  aperture) .  In  the  outer  coat  of  the  gemmule  observe 
spicules  which  differ  markedly  from  the  skeleton  spicules 
in  form.  These  gemmule  spicules  vary  greatly  in  form  in 
different  fresh- water  sponges.  If  the  sponge  named  at  the 
beginning  of  this  section  furnished  the  gemmules  now 
under  examination,  the  spicules  found  in  their  outer  coat 
will  be  of  the  form  of  a  spool,  with  the  discoidal  ends  of 
the  spool  notched  to  form  radiating  points,  and  with  the 

1  This  preparation  and  the  one  following  it,  the  student  may  make  for 
himself,  if  desired,  by  following  directions  found  in  Appendix,  p.  280. 


24  CCELENTERATES. 

slender  axis  of  the  spool  produced  into  a  short  point 
(umbonate)  at  each  end.  The  axes  of  these  spicules  are 
directed  toward  the  center  of  the  gemnmle,  so  that,  on 
looking  at  the  surface  of  the  gemmule,  only  the  radiate 
disks  on  the  distal  end  of  the  spicules  are  seen.  Looking 
at  the  cut  edge  of  the  outer  coat  of  a  gemmule  which 
has  been  divided  in  halves,  a  lateral  view  of  some  of  the 
spicules  will  be  obtained,  and  their  somewhat  spool-shaped 
(birotulate)  outline  will  be  recognized. 

For  a  better  view  of  both  skeleton  and  gemmule  spic- 
ules, examine  some  which  have  been  isolated  with  nitric 
acid  and  mounted  separately.  Draw  typical  spicules  of 
both  kinds. 

Make  an  outline  drawing  of  the  whole  sponge.  Fill  in 
the  details  in  a  part  of  the  drawing  so  as  to  show  osteoles, 
pores,  and  gemmules. 

The  gemmules  are  reproductive  bodies ;  and  their  outer 
coats,  strengthened  with  beautiful  spicules,  however  inter- 
esting in  themselves,  are  of  value  to  the  sponge  only  as 
they  form  a  protective  covering  for  the  protoplasmic  con- 
tents of  the  gemmule.1  When,  in  winter,  the  old  sponge 
dies  down,  and  the  gemmule  has  been  set  adrift,  the 
protoplasmic  cells  of  its  interior  in  some  favoring  situa- 
tion escape  through  the  aperture,  associate  and  attach 
themselves  in  a  relatively  compact  mass,  and  begin  to 
take  food  from  the  surrounding  water,  and  to  grow  up 
into  a  new  sponge. 

In  watching  the  development  from  gemmules,  note  the 
following.2 

1.  The  protoplasmic  contents  of  the  gemmule  may  be 
seen  to  issue  by  amoeboid  efforts,  to  grow  and  develop  sar- 

1  The  gemmule  is  formed  (Marshall)  by  a  number  of  free  amoeboid 
sponge  cells  which  come  together  at  some  point  in  the  sarcode,  and  secrete 
a  thin  pellicle  about  themselves.     The  surrounding  cells  secrete  the  outer 
coat  of  the  gemmule,  with  its  supporting  spicules. 

2  For  methods  of  preparation  for  this,  see  Appendix,  p.  281. 


THE   FRESH-WATER    SPONGE.  25 

code  with  its  supporting  spicules,  its  pores,  osteoles,  and 
communicating  canals.  The  abundant  secretion  of  sili- 
ceous spicules  by  this  simple  protoplasmic  mass,  and  the 
arrangement  of  them  in  definite  lines  to  form  a  skeletal 
structure,  are  easily  seen,  and  are  somewhat  remarkable 
phenomena. 

2.  The  sarcode  masses  produced  from  few  or  many 
separate  gemmules  may  be  seen  to  meet  and  coalesce  to 
form  a  single  sponge,  showing  further  the  aggregate  nature 
of  the  animal. 

The  Life  Process.  —  When  the  amoeba  divides,  its  cells 
separate  as  independent  animals ;  but  when  the  pr.oto- 
plasmic  mass  of  .the  sponge  gemmule  divides  off  new 
cells,  these  cells  remain  aggregated  together.  Although 
they  arrange  themselves  so  as  to  inclose  water  canals 
when  their  whole  mass  becomes  too  great  for  contact  of 
all  parts  with  the  water,  and  although  they  cooperate  in 
the  formation  of  spicules  in  more  or  less  definite  lines, 
they  yet  lead  in  some  respects  an  independent  existence, 
in  that  each  cell  lives,  eats,  assimilates,  grows,  excretes, 
and  divides  for  itself.  The  life  process  in  each  cell  is 
therefore  not  greatly  different  from  that  of  the  single 
cell  of  amoeba,  save  that  the  sponge  cell  is  more  limited  in 
its  search  for  food,  being  compelled  to  take  such  as  the 
water  currents  bring  to  it.  But  this  loss  of  power  to  the 
single  cell  is  obviously  to  the  advantage  of  the  sponge  as 
a  whole.  And  just  in  proportion  as  the  individual  cells 
lose  their  individuality,  and  become  arranged  and  ordered 
for  the  good  of  the  animal  they  compose,  the  animal  ceases 
to  be  a  mere  aggregate  of  cells,  and  becomes  an  integrate 
organism. 

Differentiation  is  the  term  applied  to  the  way  cells  have 
of  growing  different,  —  of  becoming  unlike  in  form  when 


26  CCELENTERATES. 

combined  together  to  form  an  animal  of  more  than  one 
cell  (a  metazoari).  Thus  the  ciliated  cells  in  the  water 
cavities  of  the  sponge  have  become  differentiated  from 
those  which  possess  no  cilia.1 


THE  HYDRA. 

(Hydra  viridis  ?) 

Study  of  Live  Specimens.  —  In  an  aquarium  or  glass 
jar  in  which  hydras  are  kept2  study  the  creatures  alive. 
Observe :  — 

1.  Their  shape,  —  elongated,  cylindrical,  Avith  the  body 
attached  at  its  posterior  or  foot  end  to  some  support,  free 
at  its  anterior  end,  and  crowned  with  a  circle  of  long, 
radiating  tentacles. 

2.  Their  color. 

3.  Their  position:  if  all  are  in  the  same  position;  if  all 
are  attached  to  the  same  kind  of  a  support;  in  what  part 
of  the  vessel  they  are  most  numerous. 

4.  Their  actions.     Note  the  swaying-about  of  the  long 
tentacles  in  the  water.     These  capture  food.     A  minute 
animal  that  has  been  captured  may  sometimes  be  seen, 
before   it   is   carried  to    the   mouth,  sticking  to   one  of 
the  tentacles.     Touch  the  tentacles,  and  see  them  con- 
tract. 

If  the  hydra  jar  be  so  placed  that  light  reaches  it 
strongly  from  but  one  side,  after  some  time  the  hydras 
which  are  on  the  opposite  side  of  the  jar  will  move 
toward  the  light,  when  their  slow  and  very  peculiar  loop- 
ing locomotion  may  be  seen. 

1  For  a  further  study  of  this  and  of  related  sponges,  the  student  is  re- 
ferred to  Potts's  Monograph  of  Fresh-Water  Sponges.     For  a  good  dis- 
cussion of  the  relations  and  differences  between  plants  and  animals,  he  is 
referred  to  Parker's  Elementary  Biology. 

2  See  Appendix,  p.  282. 


THE   HYDRA.  27 

5.    Their  three  methods  of  reproduction :  — 

(a)  By  buds.  These  are  blunt  processes  often  seen 
sticking  out  at  right  angles  to  the  body  of  the  parent 
hydra,  outgrowths  from  its  sides,  destined  to  become  perfect 
hydras,  and,  when  well  grown,  to  separate,  and  lead  an 
independent  existence.  All  stages  of  the  budding  process 
may  usually  be  found,  from  the  incipient  bud  without 
tentacles,  to  the  fully  formed  hydra  ready  to  drop  away. 

(5)  By  true  sexual  organs,  —  minute  cone-shaped  or 
dome-shaped  eminences  on  the  sides  of  the  body,  just 
visible  without  a  lens. 

(c)  By  a  sort  of  vegetative  reproduction,  like  the  starting 
of  a  new  plant  from  a  slip  or  cutting  taken  from  an  old 
one.  To  see  this  will  require  a  carefully  conducted  exper- 
iment, costing  a  little  time  and  trouble,  but  worth  both. 
Cut  out  a  piece  of  leaf  with  three  hydras  on  it,  and  place 
it  and  them  in  a  separate  vessel  of  water.  With  a  pair 
of  thin,  sharp  scissors,  cut  off  a  tentacle  from  one  of  the 
hydras,  to  see  it  reproduced.  Cut  the  second  hydra  in  two 
crosswise,  and  slit  the  third  one  into  two  pieces  length- 
wise. If  properly  done,  the  pieces  will  live,  and  each 
will  develop  into  a  perfect  hydra.  The  progress  of  these 
specimens  should  be  watched  daily,  and  as  much  oftener 
as  is  convenient. 

Detach  a  hydra  from  its  support,  take  it  up  with  a 
dropping  tube,  and  place  it  in  a  watch  crystal  containing 
water  under  the  microscope,  and  examine  with  low  power. 
Observe  :  — 

1.  The  broad  or  flattened  foot  by  which  it  was  attached. 

2.  The  flexible  cylindrical   body  (often   distended   in 
places  by  food,  or  extended  into  buds). 

3.  The  tentacles:  their  number;  their  knotted  appear- 
ance ;  their  action. 

4.  The    cone-shaped   prominence    (hypostome)    at   the 
anterior  end,  between  the  bases  of  the  tentacles. 


28  CCELENTERATES. 

5.  The  mouth,  which  is  at  the  top  of  this  prominence, 
and  may  be  seen  in  favorable  positions;  i.e.,  when  it  is 
turned  upward  and  opened. 

Structure.  —  Mount  the  hydra  alive  in  a  drop  of  water 
upon  a  slide.  Place  two  minute  slips  of  paper  or  two 
threads  alongside  the  hydra,  and  lower  a  cover  glass  upon 
these.  Examine  first  with  low,  and  afterward  with  higher 
power,  to  make  out  the  following  points  of  structure  :  — 

1.  The  body  is  a  hollow  tube  with  but  one  opening  to 
the  exterior,  the  mouth.     The  interior  of  this  tube  is  the 
gastric  cavity.     Observe  that  this  cavity  extends  out  into 
the  buds,  when  present,  and  into  the  tentacles.     When 
the  tentacles  are  fully  extended,  food  particles  may  be 
seen  in  them. 

2.  The  body  Avail  is  double.     Its  outer  coat  (the  ecto- 
derm) is  made  up  of  small  transparent  cells ;    its  inner 
coat  (the  endoderm),  of  larger,  darker  cells.     The  body  is 
therefore  a  double-walled   sac,  both  walls  of   which  are 
pushed  outward  to  form  buds  and  tentacles. 

3.  In  the  ectoderm,  in  parts  of  the  body,  and  especially 
in  the  swollen  parts  of  the  tentacles,  are  certain  conspic- 
uous  round   or  oval  cells   surrounded  by  smaller  ones. 
These  larger  ones  are  called  thread  cells,  lasso  cells,  or 
nettle  cells,  because  they  contain  a  long,  spirally  coiled 
thread,  which  can  be  thrown  out  at  will,  and  is  used  in 
capturing  prey.     When  the  long,  swaying  tentacles  ap- 
proach some  animal  suitable  for  food,  as  a  water  flea,  these 
threads  are  thrown  out,  and,  coming  in  contact  with  the 
flea,  they  seem  to  paralyze  it.    It  hangs  apparently  stunned, 
adhering  to  several  of  these  threads,  and  is  quickly  swept 
into  the  mouth.     If  a  drop  of  acetic  acid,  magenta,  or 
methyl  green  be  drawn  under  the  cover  glass,  and  the  ten- 
tacles watched  at  the  same  time,  the  throwing-out  of  these 
threads  may  be  seen.     Afterward  some  of  these  lasso  cells 


THE    HYDRA. 


29 


may  be  found  entirely  dislodged  from  the  tentacle,  and 
showing,  beside  the  long  stinging  filament,  a  flask-shaped 
base,  with  minute  retrorse  spines  at  the  neck  of  the  flask 
whence  the  filament  springs. 

4.  The  sexual  reproductive  elements  are  developed  in 
low  elevations  upon  the  sides  of  the  body.  These  are  of 
two  kinds  :  — 

(a)  Spermariet,  —  conical,  pointed  elevations  near  the 
anterior  end  of  the  body,  just  behind  the  tentacles,  of 


HYDRA  (X  6) :   m,  mouth;  sp,  spermaries ;  ov,  ovary;  b,  bud. 

variable  number.  In  the  transparent  apex  of  a  ripe  sper- 
mary,  the  sperms  may  be  seen  swimming  actively  about  or 
breaking  out  into  the  surrounding  water. 

(6)  Ovaries,  —  rounded,  obtuse  elevations  nearer  the 
foot,  rather  larger  than  spermaries  when  ripe,  usually 
fewer  in  number,  and  each  containing  but  a  single  ovum. 

Both  spermaries  and  ovaries  are  developed  from  the 
ectoderm,  as  might  be  inferred  from  their  position  and 
from  their  transparency. 


30  CCELENTERATES. 

Sexual  Reproduction  consists  in  the  production  of  male 
and  female  reproductive  elements,  sperms  and  ova,  and  in 
their  union  to  form  oosperms,  and  in  the  development  of 
the  oosperms  into  new  individuals.  At  first  certain  cells 
are  separated  off  from  the  other  cells  of  the  body,  and  in 
certain  parts  of  the  body,  specialized  for  the  purpose,  are 
developed  into  sperms  and  ova.  Then  the  sperms  of  the 
hydra  escape  out  into  the  water,  and  swim  actively  about 
until  some  of  them  come  into  contact  with  the  ova  of 
another  hydra.  One  sperm  enters  and  coalesces  with 
each  ovum,  changing  it  into  an  oosperm.  Fertilization 
is  the  name  for  this  part  of  the  process.  The  resultant 
oosperm  hardly  differs  from  the  ovum  in  appearance,  yet 
vitally  differs  from  it,  in  that  the  oosperm  has  the  poten- 
tiality to  become,  under  proper  conditions,  a  new  hydra. 

When  both  kinds  of  sexual  elements  are  produced  in  a 
single  individual,  the  individual  is  said  to  be  hermaphro- 
dite. In  the  hydra,  spermaries  are  developed  first;  and 
not  until  after  they  are  ripened,  and  their  sperms  dis- 
charged, do  the  ovaries  mature  their  ova.  The  ova  can- 
not, therefore,  be  fertilized  by  sperms  from  the  same 
individual,  but  Avill  be  fertilized  by  sperms  of  a  later 
growth  from  some  other  individual.  This  is  called  cross 
fertilization :  it  seems  to  be  essential  to  the  healthy  con- 
tinuance of  most  animals. 

The  Life  Process.  I.  Nutrition. — In  the  hydra  we 
have  our  first  example  of  an  animal  with  a  distinct  gastric 
cavity,  in  which  food  may  be  received  and  retained  until 
digested.  We  find,  also,  better  means  of  securing  food  than 
in  any  protozoans.  After  the  food  is  taken  by  the  tenta- 
cles and  the  extensible  mouth,  it  is  pressed  down  into  the 
digestive  cavity,  and  there  the  endoderm  cells  do  most,  if 
not  all,  of  the  work  of  reducing  it  to  soluble  form.  These 
lining  cells  are  large,  and  capable  of  considerable  amoeboid 


THE   HYDRA.  31 

motion,  which  may  be  seen  in  thin  transverse  sections 
cut  from  a  living  specimen.  Their  combined  motions 
probably  have  much  to  do  with  comminuting  the  food. 
Their  secretions  probably  act  on  it  chemically  to  digest 
it;  but  when  it  is  digested,  it  must  pass  out  to  all  parts 
of  the  body  by  simple  osmosis  from  cell  to  cell,  and  by 
the  slight  propulsion  given  by  the  moving  of  the  parts 
of  the  body  upon  one  another,  for  there  are  no  circulating 
vessels.  There  being  but  one  external  opening  to  the 
digestive  tract,  the  indigestible  portion  of  the  food  must 
be  cast  out,  as  it  is  taken  in,  through  the  mouth.  The 
absorption  of  free  oxygen  and  of  mineral  foods  in  solu- 
tion in  the  water,  takes  place  directly  through  the  body 
wall.  The  assimilation  of  these  various  foods  from  vari- 
ous sources,  the  building  of  them  into  the  body  structure, 
and  the  removal  of  the  waste  products  of  activity, — 
these  things,  in  hydra,  as  in  all  animals,  each  cell  does 
for  itself. 

II.  Reproduction.  —  That  .the  hydra  is  hermaphrodite 
has    already    been    seen,    and    also    that    it    reproduces 
greatly  by   budding.       Did    these   buds   remain   perma- 
nently attached,  as  in  some  of  the  hydra's  marine  rela- 
tives,  instead   of    falling   away   when   fully   grown,   we 
should    have    it    developing    a    peculiar    treelike    form. 
Hydra  does  not  divide  of  itself  into  two  equal  parts,  but, 
when  so  divided  artificially,  the  parts  may  each  become 
a  new  hydra  with  all  lost  parts  reproduced.     Pieces  much 
smaller  than  half  the  animal  may  grow  into  perfect  hy- 
dras.    It  seems  to  be  only  necessary  that  all  the  essential 
structures  be  represented,  and  probably  is  most  essential 
that  the  ectoderm  (the  reproductive  layer)  and  the  erido- 
derm  (the  digestive  layer)  be  present  and  in  their  proper 
relations  together. 

III.  Voluntary  Motion.  —  The  hydra  is  another  of  the 
animals   that    "move  without   muscles."     Yet  its  move- 


32  CCELENTERATES. 

ments  are  varied  and  interesting.  They  are  ceaseless, 
too,  as  may  be  seen  by  watching  its  continually  changing 
form.  Though  all  its  individual  cells  have  the  power 
of  motion,  some  cells,  as  those  in  the  tentacles,  move 
more  freely  than  others.  The  lasso  cells  are  capable 
of  a  very  sudden  and  remarkable  and  highly  specialized 
act,  —  the  thro  wing-out  of  their  paralyzing  filament. 

IV.  Sensation.  —  No  nervous  system  is  developed  in  the 
hydra;  but  a  few  nerve  cells,  developed  between  the  bases 
of  the  ectoderm  cells,  are  known  to  exist.  There  is  a 
marked  advance  in  the  powers  of  sensation  of  this  animal 
over  those  previously  studied,  seen  in  greater  reaction 
from  disturbances,  in  greater  skill  in  securing  food  and 
more  choice  in  selecting  it,  in  preference  for  light,  etc. 

Tissue  and  Organ.  —  The  cells  of  the  ectoderm  in 
hydra,  being  much  alike  in  form  and  in  the  work  they 
have  to  do,  constitute  a  primitive  tissue.  The  cells  of  the 
endoderm  constitute  another  such  tissue.  A  tissue  may 
be  defined  as  an  aggregation  of  similar  cells,  together  with 
whatever  intercellular  substance  may  be  developed  from 
the  cells. 

When  any  part  of  an  animal  is  set  apart  for  a  particular 
work,  that  part  is  called  an  organ,  and  the  work  it  has  to 
do  is  called  its  function.  Thus  the  tentacles  of  the  hydra 
are  organs,  and  their  function  is  reaching  out  after  food. 

Differentiation  becomes  very  evident  in  the  hydra. 
The  thread  cells  of  the  tentacles  are  very  unlike  the 
digestive  cells  of  the  endoderm  in  the  digestive  cavity. 
In  the  work  they  have  to  do,  there  is  quite  as  great  dif- 
ference as  in  their  form.  The  thread  cells  are  given  a 
specific  work  to  do,  —  the  capturing  of  food.  Other  cells 
do  the  digesting,  and  can  do  it  better  for  being  relieved 
of  the  work  of  capturing  the  food.  This  is  what  is  meant 
by  a  physiological  division  of  labor.  This  sort  of  spe- 


THE   HYDRA.  33 

cialization,  so  evident  in  the  development  of  animals,  has 
its  parallel  in  the  development  of  civilization  or  in  the 
development  of  a  trade.  For  example,  the  early  cobbler 
tanned  his  own  leather,  whittled  his  own  pegs,  made  his 
own  thread,  lasts,  etc.,  and  then  made  the  shoe.  But,  as 
the  trade  of  shoemaking  developed,  one  man  began  giving 
his  whole  time  to  making  the  leather ;  another,  to  making 
the  lasts,  etc. ;  and  another,  to  making  the  shoe.  To  see 
how  much  further  than  this  the  division  of  labor  in  shoe- 
making  has  gone  in  our  own  time,  we  need  only  to  visit  a 
modern  shoe  factory. 

When  the  cobbler  gave  up  to  the  tanner  the  making  of 
the  leather,  he  became  a  more  skillful  shoemaker,  but  lost 
his  skill  at  tanning.  So,  when  the  thread  cell  of  the 
hydra  becomes  differentiated  for  capturing  food,  it  excels 
in  that  one  thing,  but  it  loses  its  capacity  for  doing  other 
things.  Here  we  come  upon  the  universal  principle,  that 
precise  adaptation  to  any  one  thing  involves  limitations  in 
other  things. 

Division  of  labor  develops  greater  skill  and  better 
products  in  a  trade,  higher  powers  and  capacities  in 
animal  life.  While  there  are  many  things  which  cells 
and  cobblers  may  leave  to  be  done  by  others,  to  the  ad- 
vantage of  all  concerned,  there  are  yet  other  things  which 
each  must  continue  to  do  individually.  For  example,  the 
thread  cell,  though  it  may  be  relieved  of  the  work  of 
digesting  its  food,  must  continue  to  absorb  the  digested 
food  as  it  is  furnished,  and  assimilate  it;  must  absorb 
oxygen,  and  must  excrete  waste  oxidized  materials  for 
itself,  so  long  as  it  continues  a  living  cell. 

The  hydra  and  the  sponge  are  representations  of  the 
Coelenterata,  a  large  and  important  group  of  animals, 
almost  exclusively  marine. 

NEED.  ZOOL.  — 3 


INSECTS. 


Collecting. — Insects  are  abundant  in  nearly  all  locali- 
ties throughout  the  interior  of  the  United  States.     There 
need,  therefore,  be  no  lack  of  material  at  the  proper  sea- 
son.   And  because  this  group  illustrates  well  the  principles 
of    zoology,   and   furnishes   animals   of 
singular  beauty,  variety,  interest,  and 
importance,  it  may  profitably  be  studied 
as  long  as  the  limitations  of  time  will 
permit. 

Three  special  pieces  of  apparatus  will 
be  needed,  —  a  collecting  net,  a  cyanide 
bottle,  and  a  collecting  basket. 

The  net  is  for  catching  insects.  To 
make  it,  get  a  light,  wooden  handle  two 
or  three  feet  long,  a  piece  of  heavy  wire 
(about  No.  8)  two  feet  and  a  half  long, 
several  feet  of  small  wire  (broom  wire 
will  do),  and  a  square  yard  of  "  Swiss  " 
or  mosquito  netting.  Bend  the  heavy 
wire  in  a  circle,  crossing  the  ends  and 
bending  them  parallel.  Cut  a  groove 
in  the  end  of  the  handle,  and  continue 
it  down  the  sides.  Place  the  crossed  ends  of  the  wire  in 
this  groove  on  opposite  sides  of  the  handle,  and  wrap  them 
there  securely  with  the  small  wire.  Make  a  bag  of  the 
netting,  of  the  same  diameter  as  the  wire  circle,  and  about 
two  feet  deep.  Sew  this  on  the  wire  circle,  and  the  net  is 
complete.  With  a  very  little  practice,  it  can  be  used  suc- 

34 


FRAME  FOR  INSECT 
NET:  a,  loop  of 
wire;  b,  handle; 
c,  wire  and  han- 
dle in  place. 


COLLECTING  35 

cessfully.  When  by  a  stroke  the  insect  is  caught,  a  quick 
turn  of  the  hand  makes  a  fold  in  the  net,  and  prevents 
its  escape. 

The  cyanide  bottle  is  for  killing  insects  that  are  to 
be  preserved  as  specimens.  Get  a  wide-mouthed  bottle 
of  a  capacity  of  at  least  a  pint,  half  an  ounce  of  potas- 
sium cyanide,  a  handful  of  plaster  of  Paris,  and  a  poison 
label.  Break  the  cyanide  into  small  pieces  (avoid  its 
poisonous  fumes),  and  place  them  in  the  bottom  of  the 
bottle.  Pour  in  just  enough  water  to  cover  them.  Add 
plaster  of  Paris  until  it  remains  dry  over  the  entire  sur- 
face. The  plaster  will  quickly  set,  forming  a  porous 
poison  cake  in  the  bottom.  Let  the  bottle  stand  uncorked 
for  half  a  day;  then  shake  out  the  surplus  plaster,  wipe 
clean  the  sides,  cork,  affix  the  poison  label,  and  keep  out  of 
the  way  of  children.  Most  insects,  when  shut  inside,  die 
at  once.  To  transfer  a  captured  insect  from  the  net  to  the 
bottle,  push  the  uncorked  bottle  carefully  up  inside  the 
folded  net. 

The  collecting  basket  is  for  carrying  insects  home  alive. 
A  close-woven  basket  with  a  netting  cover  will  answer 
every  purpose.  Any  kind  of  basket  will  do,  if  lined  with 
netting.  A  place  must  be  fixed  at  the  edge  for  putting  in 
and  taking  out  the  insects. 

In  collecting,  always  observe  the  following  rules :  — 

1.  Collect  no  more  specimens  than  will  probably  be  used. 
The  taking  of  more  is  but  the  wanton  destruction  of  life. 

2.  Get  for  preservation  the  finest  specimens  obtainable, 
and  preserve  them  with  utmost  care.     Fine  specimens  are 
always  a  delight,  and  poor  ones  are  of  no  credit  to  any  one. 

3.  Keep  live  specimens  supplied  with  food,  water,  and 
fresh  air.     To  let  an  animal  die  a  lingering  death  for  want 
of  either  of  these  common  necessities,  is  extreme  cruelty. 

4.  Make  each  collecting  trip  an  opportunity  for  study- 
ing animal  life  under  natural  conditions.     Make  note  of 


36  INSECTS. 

the  haunts  of  each  animal,  of  its  animal  associates,  of  its 
food,  of  its  shelter,  of  its  natural  enemies,  of  its  home,  — 
in  short,  of  the  life  it  leads.  Such  study  will  lead  to 
important  general  truths  relating  to  all  animal  life,  includ- 
ing that  of  man,  and  is  best  begun  in  the  field. 

5.  Remember  that  fear  is  inherent  in  most  animals,  and 
that  flashy  colors,  loud  noises,  and  quick  and  careless  move- 
ments will  frighten  them,  and  cause  the  loss  of  opportuni- 
ties for  observation.  Hence  wear  quiet  colors,  avoid 
noise,  avoid  haste,  and  keep  your  eyes  wide  open. 


HEXAPOD  INSECTS. 

THE  BUTTERFLY. 
(A  PRELIMINARY  LESSON.) 

Characteristics. — The  common  sulphur  butterfly  (Eury- 
mus  philodice J)  will  serve  well  for  a  beginning  in  the  study 

of  insects.  It  may  be  known  by  its 
yellow  wings  bordered  with  black, 
and  by  a  silvery  spot  set  in  a  patch 
of  pinkish  brown  on  the  lower  sur- 
face of  the  hind  wings.  Like  other 
butterflies,  it  may  best  be  collected 
about  midday.  Any  clover  field 
or  meadow  will  probably  furnish  a 

supply.     Any  other  butterfly  that 
THE   SULPHUR   BUTTERFLY, 

Eurymus  philodice  (natu-    can  easily  be  collected  will  answer 
ralsize)«  the  present  purpose  quite  as  well. 

Study  of  Live  Specimens. —  Collect  specimens  for  imme- 
diate use  and  for  preservation,2  and  while  collecting  study 
the  living  butterflies  and  their  haunts  and  habits,  noting :  — 

1  Colias  philodice  of  some  authors. 

2  Observe  that  all  the  specimens  captured  are  not  in  equally  good  con- 


THE   BUTTERFLY.  37 

1.  The  species  of  the  flowers  on  which  you  find  them 
feeding. 

2.  The  manner   of   their  feeding:   whether  they,  like 
humming  birds,  obtain  their  food  while  on  the  wing. 

3.  The  kind  of  food:  it  is  the  nectar  of  the  flowers, 
the  raw  material  for  honey.     To  prove  its  presence  in  the 
flowers,  pluck  a  few  corollas  from  a  head  of  red  clover, 
and  press  their  bases  between  your  lips :   you  will  taste 
the  sweet  nectar. 

4.  The  organ  used  in  obtaining  this  food :  its  position 
when  in  use  and  when  not  in  use ;  its  shape;  its  length. 

5.  The  natural  enemies  of  the  butterfly;  to  what  dan- 
gers its  life  is  commonly  exposed. 

6.  Its  animal  associates;    with  what  other  animals  it 
shares  its  food. 

When  you  get  home,  liberate  a  live  butterfly  before  a 
closed  window,  and  study  its  motions. 

Observe:    1.  The  position  of  its  wings  when  at  rest. 

2.  The  unity  of  their  action  when  in  motion. 

3.  Its  irregular  flight. 

4.  Its  jerky  walk. 

5.  The  number  of  its  feet;  the  number  moved  at  a  time 
while  walking. 

Take  time  to  admire  the  beauty  and  harmony  of  its 
form  and  coloration,  the  alertness  of  its  posture,  and  the 
exquisite  velvet  of  its  wings. 

It  is  at  once  apparent  that  in  its  activities  and  capacities 
the  butterfly  far  surpasses  amoeba,  sponge,  and  hydra.  The 
first  few  steps  up  the  grade  of  animal  life  we  took  in  their 
proper  order;  but  now,  for  the  sake  of  convenience,  we 

dition.  Some  have  their  wings  rubbed  and  torn.  Place  such  in  the  bas- 
ket, and  take  them  home  for  further  study  alive.  Put  the  best  in  the 
cyanide  bottle.  It  is  well  to  have  two  cyanide  bottles,  —  one  to  kill  and 
one  to  carry  specimens  in, — for  the  fluttering  of  live  specimens  put  into 
the  bottle  may  rub  and  mar  the  beauty  of  former  captives  which  have  not 
been  removed.  See  note  on  mounting  insects,  in  Appendix,  p.  283. 


38 


INSECTS. 


ant 


pass  by  those  which  would  succeed  in  logical  order,  to 
study  a  group  of  animals  that  is  highly  specialized. 

Plan  of  Structure.  —  A  superficial  study  of  the  external 
features  of  the  butterfly  will  give  a  general  idea  of  the 
insect  plan  of  'structure.  Examine  a  butterfly  which  has 
been  killed  in  the  cyanide  bottle,  and  observe  its  horny 
incasement,  —  an  outside  skeleton  covering  the  whole  sur- 
face, but  thickest  and  hardest  on  those  parts  of  the  body 

most  exposed.  This 
is  a  very  different 
exterior  from  that 
of  the  sponge  or  the 
hydra  :  such  ani- 
mals, if  exposed  to 
the  air,  would  soon 
die  of  evaporation, 
if  from  no  other 
cause.  This  hard 
exterior  is  an  adap- 
tation to  aerial  life, 
as  well  as  a  protec- 
tion against  injury. 
This  coat  of  mail  in 
insects  is  an  out- 
growth from  the  skin,  and  is  composed  of  a  horny  sub- 
stance called  chitin.  It  is  very  light  and  very  tough,  — 
two  important  requisites  in  the  armor  of  a  flying  animal. 

Place  the  butterfly  in  its  erect  position,  with  the  head 
away  from  you,  and  compare  the  right  and  left  sides  with 
reference  to  the  arrangement  of  parts.  Observe  that 
the  parts  correspond,  that  the  sides  are  symmetrical. 
Bilateral  symmetry  is  the  term  used  in  zoology  to  desig- 
nate such  arrangement  of  parts.  What  animals  have  you 
seen  that  are  not  bilaterally  symmetrical  ? 


trn 


DIAGRAM  OF  SULPHUR  BUTTERFLY  (X2),  de- 
nuded of  scales,  right  wings  removed: 
h,  head;  1,  prothorax;  2,  mesothorax; 
3,  metathorax;  a,  abdomen;  w  I,  left  fore 
wing;  w  2,  left  hind  wing;  black  ™'s  indi- 
cate the  points  of  attachment  of  right  wings ; 
ant,  antenna ;  e,  eye  ;p,  palpus ;  m,  "tongue ;" 
ex,  coxae  of  right  legs ;  tr,  trochanter  of  right 
hind  leg ;  /,  femur ;  t,  tibia ;  trs,  tarsus  or 
foot. 


THE   BUTTERFLY.  39 

Observe  that  there  are  three  somewhat  distinct  regions 
in  the  body.  These  are  named,  in  order,  head,  thorax,  and 
abdomen. 

Observe  that  the  entire  body  is  made  up  of  rings  or  seg- 
ments. How  many  segments  are  there  in  the  thorax?  In 
the  abdomen? 

Note  now  the  external  parts  and  appendages. 

1.  The  Head.  — 1.    The  long  projections  on  the  front  of 
the  head  are  antennae.     These  also  have  segmented  struc- 
ture.    Study  them  with  the  aid  of  a  lens,  and  count  their 
segments. 

2.  The  large  hemispherical  prominences  on  the  sides 
of  the  head  are  the  eyes,  called  also  facets  or  compound 
eyes,  because  they  appear  under  magnification  to  be  made 
up  of  clustered  simple  eyes  placed  side  by  side. 

3.  The  two  more  or  less  hairy  appendages  in  front  of 
and  below  the  eyes  are  the  labial  palpi.     Count  their  seg- 
ments, and  find  their  point  of  attachment  to  the  head. 

4.  The  coiled  organ  between  the  palpi  is  the  sucking 
organ  (or  proboscis) .     Uncoil  it :  how  many  turns  in  it  ? 
Notice  the  permanent  bend  near  the  middle  of  it.     Ob- 
serving that  there  is  no  oral  opening  on  the  surface  of 
the  head,  what  structure  will  you  expect  to  find  within 
this  proboscis? 

With  the  microscope  examine  :  — 

1.  A  cross  section  of  the  proboscis.1 

2.  A  tangential  section  of  the  surface  (corneal  layer) 
of   the  eye.2     Observe  that  the  corneal   layer  seems   to 


1  To  make  the  cross  section,  place  the  proboscis  uncoiled  in  a  split 
cork  or  between  two  pieces  of  elder  or  cornstalk  pith,  and,  holding  it 
firmly  there,  with  a  razor  or  a  very  sharp  knife  shave  off  thin  sections  at 
the  end,  shaving  the  holder  and  the  proboscis  together. 

2  Cut  a  section  from  the  surface  of-  the  eye.     Holding  the  section  with 
fofceps  by  one  edge,  scrape  out  the  dark-colored  pigment  from  its  inner 
concave  surface.     Place  it  on  a  slide,  convex  surface  uppermost,  and  it 
is  ready  for  examination.    Use  low  power. 


40  INSECTS. 

be  composed  of  many  hexagonal  corneas.  Make  a  draw- 
ing of  a  portion  of  it  as  seen  under  the  microscope. 
Count  the  corneas  in  a  certain  visible  space.  Estimate 
what  part  this  space  is  of  the  whole  corneal  layer,  and 
calculate  the  number  of  corneas  in  the  whole  layer. 

II.  The  Thorax. — Note  that  the  thorax  is  composed  of 
three  segments. 

1.  The  small  first  segment,  to  which  the  first  pair  of 
legs  is  attached,  is  the  prothorax. 

2.  The  large  second  segment,  to  which  the  second  pair 
of  legs  and  the  first  pair  of  wings  are  attached,  is  the 
mesothorax. 

3.  The  third  segment,  to  which  the  third  pair  of  legs 
and  the  second  pair  of  wings  are  attached,  is  the  meta- 
thorax.     Owing  to 'the  consolidation  of  meso-  and  meta- 
thorax,  the   boundary  between   these  segments  may  not 
be  very  plainly  seen. 

Observe  that  the  thorax  is  in  cross  section  more  or  less 
quadrangular,  showing  more  or  less  flattened  dorsal,  lateral, 
and  ventral  surfaces.  The  dorsal  surface  is  called  the 
notum,  each  lateral  surface  a  pleurum,  and  the  ventral 
surface  the  sternum.  The  convenience  of  this  notation 
will  be  seen  in  the  ease  with  which,  by  using  it,  any  part 
of  the  thorax  may  be  designated.  The  upper  or  lower 
part  of  the  prothorax  may  be  referred  to  as  pronotum  or 
prosternum ;  corresponding  parts  of  the  metathorax,  as 
metanotum  or  metasternum,  etc. 

Examine  one  of  the  legs.  Note  that  it,  too,  is  made  up 
of  segments,  which,  like  those  of  the  body,  have  a  hard 
outer  shell  of  chitin.  Flex  and  extend,  and  study  the 
action  of  the  joints. 

1.  The  first  small  segment,  the  one  by  which  the  leg 
articulates  with  the  body,  is  the  coxa. 

2.  The  next  is  a  very  small  quadrangular  segment,  not 
always  easily  made  out,  the  trochanter. 


THE   BUTTERFLY.  41 

3.  The  next  is  the  largest  segment  of  the  leg,  the  femur. 

4.  The  next  is  a  slender  segment  about  as  long  as  the 
femur.     It  is  the  tibia. 

5.  The  remaining  segments  comprise  the  foot  (or  tarsus). 
Count  these  tarsal  segments.     Note  what  appendages  are 
present,  and  on  which  segments.     Examine  the  lower  sur- 
face   of   these  segments.     Discover   by  what  means  the 
butterfly  is  able  to  walk  on  the  lower  surfaces  of  leaves. 

Examine  the  wings,  noting:  — 

1.  Their  action. 

2.  Their  form. 

3.  Their  overlapping. 

4.  Their  covering  of  hairs  and  dust-like  scales. 

5.  Their  structure,  —  each  a  triangular  expanse  of  thin 
membrane  supported  by  chitinous  veins.      Find  five  prin- 
cipal veins  starting  outward  from  the  base  of   a  wing. 
These   are  named1  from  front  to  rear,    costal,  subcostal, 
median,  submedian,  and  internal.     Their  branches,  when 
present,  are  called  veinules  or  veinlets.     The  subcostal  and 
median  are  branched  in  butterflies.     The  costal  and  inter- 
nal are  simple.      The  internal  is  often  very  short   and 
inconspicuous  in  the  fore  wings. 

Make  a  drawing  of  the  butterfly  as  seen  from  one  side, 
with  wings  closed,  first  arranging  antennae  and  feet  in  a 
natural  position.  Make  a  drawing  of  it  as  seen  from 
above,  with  wings  extended. 

With  the  microscope  examine :  — 

1.  The  foot. 

2.  A  cross  section  of  one  of  the  larger  veins  of  the  wing. 
Rub  off  a  few  of  the  dust-like  scales  of  the  wing,  and 

examine,  first  with  moderate  and  then  with  high  power,  — 

1.  A  bit  of  the  wing  with  scales  attached. 

2.  A  bit  of  the  wing  with  scales  rubbed  off. 

3.  The  detached  scales.     Draw. 

1  See  footnote,  p.  87. 


42  INSECTS. 

III.  The  Abdomen.  —  Observe  the  form  of  the  abdomen; 
its  markings;  the  absence  of  lateral  appendages.  Count 
the  abdominal  segments,  and,  by  bending  slightly,  observe 
how  they  are  fitted  together.  Observe  a  longitudinal 
groove  on  either  side  of  the  abdomen.  Just  above  this 
groove,  in  each  segment,  is  the  opening  (more  or  less 
completely  covered  by  scales)  of  a  breathing  pore  (or 
spiracle). 

Make  a  drawing  of  the  abdomen,  lateral  view. 


THE  DRAGON  FLY. 

(Diplax.) 

Haunts  and  Habits.  —  The  young  of  the  dragon  fly  lives 
in  the  water  on  the  bottom  of  brooks  and  shallow  ponds. 
The  adults  live  in  the  air,  and  may  be  seen  through  the  day, 
poised  on  glistening  wings  above  the  water,  or  darting 
hither  and  thither  with  great  swiftness.  The  adults  may 
be  collected  with  a  net,  but  some  little  dexterity  will  be 
necessary  to  catch  the  larger  species.  A  small  brown 
species  (T)iplax  rubicundula),  with  amber-tinted  wings,  is 
abundant  in  most  places  throughout  the  interior,  and  is 
easily  captured  about  wet  meadows,  and  is  a  good  example 
for  class  use.  It  is  always  well  to  collect  a  number  of 
species  for  comparison.  While  collecting,  observe:  — 

1.  The  places  frequented. 

2.  The  habit  of  flight. 

3.  The  hours  of  flight. 

4.  The  food  sought. 

The  adult  female  dragon  fly  may  sometimes  be  seen 
hovering  low  above  the  water,  dipping  the  end  of  her 
abdomen  occasionally  beneath  the  surface,  there  deposit- 
ing eggs.  If  captured  unhurt,  and  held  gently  by  the 
fore  wings  while  the  dipping  is  done  artificially  in  a  turn- 


THE   DRAGON  FLY.  43 

bier  of  clean  water,  the  eggs  will  usually  be  deposited 
there.  They  should  be  collected  and  taken  home  in  water, 
and  their  development  studied. 

The  young  of  the  dragon  fly  are  called  nymphs.  They 
are  commonly  found  sprawling  on  the  bottom  of  shallow 
brooks  or  ponds,  or  clinging  to  submerged  trash  or  to 
aquatic  plants.  Easy  marks  of  recognition  are  the  wide 
head  and  thorax,  very  rudimentary  wings,  and  a  much- 
enlarged  and  armed  lower  lip,  which  covers  the  mouth  as 
a  shield.  A  water  net  will  capture  such  as  cling  to  sub- 
merged green  plants.  Those  found  in  trash  fallen  in  the 
water's  edge  may  be  raked  ashore  with  the  trash  and 
picked  up  by  hand,  their  active  efforts  to  return  to  the 
water  making  them  easy  to  find.  All  may  be  carried 
home  in  a  small  pail  of  water.  They  live  upon  aquatic 
insects ;  and  a  supply  of  their  insect  food  should  be  col- 
lected at  the  same  time,  and  placed  in  the  pail  with  them. 
A  few  strokes  of  a  water  net  through  a  pool  will  usually 
catch  a  supply  of  suitable  food.  A  few  submerged  green 
water  plants  should  also  be  placed  in  the  water  with  them, 
to  furnish  oxygen.  The  contents  of  the  pail  may  be 
turned  out  into  a  bowl  or  other  improvised  aquarium  at 
home,  and  there  the  nymphs  will  live  and  grow,  and 
finally  transform  into  adult  dragon  flies. 

Study  of  the  Adult.  —  Liberate  a  live  dragon  fly  in  a 
•closed  room  (it  has  no  sting,  and  is  in  no  way  hurtful  to 
man),  and  study  its  actions.  Note:  — 

1.  The  position  of  its  wings  in  motion  and  at  rest. 

2.  The  position  of  its  legs. 

If  you  can  time  its  passage  across  the  room,  make  an 
estimate  of  its  speed  in  number  of  times  its  own  length 
per  second.  Compare  this  with  the  speed  of  a  fast  horse 
reduced  to  the  same  terms. 

Put  a  live  dragon  fly  into  the  cyanide  bottle,  and  as 


44 


INSECTS. 


soon  as  it  is  thoroughly  stupefied  by  the  poison,  but  not 
killed,  turn  it  out  again  upon  a  paper,  and  study  its  re- 
spiratory movements.  Note  the  regular  expansion  and 
contraction  of  its  abdomen,  and  search  with  a  lens  for 

the  minute  openings 
of  spiracles  on  each 
abdominal  segment. 
Two  larger  spiracle 
orifices  may  be  found 
on  each  side  of  the 
thorax. 

Observe   the   spin- 
dle-shaped body;  the 


DRAGON  FLY  (natural  size). 


rounded    head,    con- 
.    cave  behind;  the  wide 
thorax;  the  angled  and  tapering  abdomen. 

I.  The  Head.  —  Note  the  enormous  development  of  the 
eyes. 

Find  a  minute  single  eye  (ocellus)  above  the  base  of  each 
antenna,  arid  another  on  the  median  line  slightly  farther 
forward. 

Remove  an  antenna  entire,  and  examine  with  a  micro- 
scope. Compare  with  the  antenna  of  a  butterfly.  Draw. 

Turn  to  the  mouth.  Find  an  upper,  movable  lip  (the 
labrum)  and  a  larger,  two-cleft,  lower  lip  (the  labiurn). 
Turn  back  the  labrum  and  the  labium,  and  find  just  beneath 
the  labrum  a  pair  of  toothed,  horny  mandibles.  Beneath- 
these  find  another  pair  of  jaws,  also  working  horizontally 
(the  maxillce).  Remove  a  maxilla  entire,  and  examine  it, 
first  with  a  lens,  and  afterward  with  low  power  of  the 
microscope.  Note  that  it  is  a  compound  organ,  made  up  of 
a  two-jointed  basal  portion  bearing  two  terminal  append- 
ages. The  inner  appendage  is  the  cutting  or  chewing  part 
of  the  maxilla  (the  lacinia,  or  blade);  the  other  append- 
age, standing  behind  or  beside  the  lacinia,  is  the  palpus. 


THE   DKAGON  FLY.  45 

If  these  parts  are  difficult  to  see,  compress  a  maxilla 
between  two  glass  slips,  and  examine  it  under  slight  magni- 
fication. Compare  this  mouth  with  the  mouth  of  a  butter- 
fly. To  what  method  of  feeding  is  this  mouth  adapted? 

II.  Thorax  and  Abdomen.  —  Find  in  thorax  and  abdomen 
all  the  parts  as  mentioned  for  the  butterfly,  noting  these 
special  points :  — 

1.  The   relative  development  of  the  thoracic  segments. 
Which  is  smallest,  and  which  largest? 

2.  The  approximation  of  the  legs.     Why  are  the  three 
pairs  thus  bunched  together;  i.e.,  what  advantage  is  there 
to  the  animal  in  such  arrangement? 

3.  The  richly  veined,  naked,  transparent  wings.     The 
costal  vein  is  on  the  anterior  margin  of  each  wing,  and  the 
subcostal  and  median  veins  are  parallel  with  it  as  far  as 
the  middle  of  the  wing.     There  a  stout  cross  vein  (the 
nodus)  crosses  these  three,  dividing  the  wing  in  halves. 
On  the  costal  margin  beyond  the  nodus  is  a  thickened 
dark  spot  (the  wing  spot,  or  ptero stigma). 

The  close  correspondence  between  the  appendages  of  the 
dragon  fly  and  those  of  the  butterfly  will  have  been  noticed 
ere  this  by  every  student.  That  the  legs  and  wings  and 
other  parts  have  essentially  the  same  structure  in  the  two 
animals,  is  very  apparent.  Had  the  origin  of  these  parts 
been  studied  in  the  developing  young  of  each  animal,  a 
similar  correspondence  would  have  been  noted.  When 
the  parts  of  two  animals  show  correspondence  in  structure 
and  origin,  such  parts  are  said  to  be  homologous;  when 
they  correspond  merely  in  use,  and  not  in  either  structure 
or  origin,  they  are  said  to  be  analogous. 

The  legs  of  a  butterfly  are  analogous  with  the  cilia  of  a 
slipper  animalcule,  because  both  structures  have  similar 
use  as  locomotive  organs ;  but  they  are  not  homologous. 
The  wings  of  the  dragon  fly  and  of  the  butterfly  are  homol- 
ogous, although  very  different  in  appearance;  for  they 


46  INSECTS. 

have  essentially  the  same  structure,  —  a  double  fold  of 
membrane  supported  by  chitiiious  veins,  —  and  they  are 
very  similar  in  development. 

Study  of  the  Nymph.  —  Place  a  large  nymph  in  a  small 
dish  with  just  enough  water  to  cover  it,  and  study  it 
alive,  with  the  aid  of  a  good  lens.  Observe  :  — 

1.  Its  sturdy  form. 

2.  Its  large  eyes. 

3.  Its  short  antennce. 

4.  Its  enormous  lower  lip,  covering  the  lower  and  front 
parts  of  the  head.     Seize  the  edge  of  it  with  fine -pointed 

forceps,  and  pull  it  forward  for  exami- 
nation. Note  that  it  is  so  jointed  to 
the  head  that  it  can  be  extended  far 
forward,  and  quickly  retracted.  Note 
that  it  is  two-lobed,  that  the  lobes  are 
triangular,  that  each  bears  an  incurved 
hook  at  the  apex,  that  each  is  toothed 
along  its  inner  margin,  and  that  the 
A  DRAGON-FLY  NYMPH,  whole  is  a  very  formidable  grasping 
organ. 

5.  Its  mouth,  with  well-developed  mandibles  and  max- 
illse  inside  the  labium. 

6.  Its  rudimentary  wings.     Compare  with  those  of  the 
adult. 

7.  Its  well-developed  legs.     Compare  them  in  position 
with  the  legs  of  the  adult. 

8.  The  regular  expansion  and  contraction  of  its  abdo- 
men in  respiration.     Note  the  striking  unlikeness  of  the 
respiratory   methods    in   the   adult   and   in   the   nymph. 
The  adult  lives  exclusively  in  the  air  ;  the  nymph,  exclu- 
sively in  the  water.     Both  must  get  oxygen  from  the 
air.    Internal  branching  and  intercommunicating  air  tubes, 
which  open  exteriorly  at  the  spiracles  in  the  adult,  con- 


THE  DRAGON  FLY.  47 

vey  currents  of  air  throughout  the  body.  But  the  nymph 
must  utilize  the  air  which  is  in  the  water,  mixed  with 
the  water,  or  held  in  solution  by  it.  To  get  this  air,  the 
water  is  alternately  drawn  into  the  abdomen  at  the  anal 
opening,  and  forced  out  again.  In  passing  in  and  out, 
the  water  flows  over  a  number  of  modified  air  passages, 
called  tracheal  gills,  which  are  situated  just  within  the 
anal  opening.1  These  tracheal  gills  have  very  thin  walls, 
easily  permeable  by  gases.  They  contain  air  to  be 
purified.  In  respiration,  osmosis  (or  exchange  of  gases 
through  the  thin  walls  of  the  tracheal  gills)  takes  place; 
carbonic-acid  and  other  noxious  gases  from  the  body 
passing  out  into  the  water,  and  oxygen  from  the  air 
contained  in  the  water  passing  in. 

To  prove  the  passage  of  water  into  and  out  of  the 
abdomen,  with  a  small  pipette  pass  a  fine  stream  of  red 
ink  or  other  colored  fluid  close  by  the  anal  opening,  and 
see  it  alternately  drawn  and  repelled  by  the  water 
currents. 

Keep  some  large  nymphs  half  a  day  without  food. 
Then  put  into  the  water  with  them  an  abundance  of  the 
insects  they  feed  upon  (such  small  ones  as  a  net  will 
catch  in  any  pond),  and  observe  how  they  capture,  hold, 
and  devour  their  prey. 

Development.  —  The  egg  hatches,  and  a  nymph  comes 
forth.  It  is  at  first  very  small ;  but  it  eats  voraciously, 
and  grows  rapidly.  It  develops  a  delicate  chitinous  coat; 
and  when  this  gets  too  small,  it  splits  down  the  back,  and 
the  nymph  crawls  out,  and  grows  another  of  larger  size. 
This  molting  takes  place  a  number  of  times  before  ma- 
turity is  reached.  On  the  bottom  of  a  vessel  in  which 
nymphs  have  been  kept  for  some  time,  a  number  of 
empty  nymph  skins  (exuvice)  may  usually  be  found. 

1  Some  species  have  external  tracheal  gills. 


48  INSECTS. 

When  the  nymph  is  fully  grown,  it  crawls  out  of  the 
water  upon  some  convenient  rock  or  reed,  and  fastens  its 
feet  firmly,  preparatory  to  the  last  and  most  remarkable 
transformation  of  all,  —  the  transformation  which  fits  it 
for  an  aerial  life. 

Keep  some  of  the  largest  nymphs,  supply  them  with 
proper  food,  and  watch  their  final  transformation. 

Make  a  series  of  drawings  of  the  egg,  of  nymphs  of 
different  sizes,  and  of  the  adult,  of  one  species.  This 
will  be  a  pictorial  life  history  of  the  species. 

The  dragon  flies  constitute  the  group  Odonata. 


THE   GRASSHOPPER. 

Haunts  and  Habits. — A  large  gray  species,  properly 
called  the  Carolina  locust  (Dissosteira  Carolina),  is  abun- 
dant by  every  roadside, 
and  will  serve  well  for 
class  use.  It  may  be  rec- 
ognized by  its  large  yel- 
low-bordered hind  wirlgs, 

exposed  in  flight.     It  may 

THE  CAROLINA  LOCUST,  Dissosteira         v      t«T,.pn    w;fu    a    ^pf     arirl 
Carolina  (natural  size).  be   taken   Wltn   a   net'    anCL 

killed  with  a  cyanide  bot- 
tle. Nymphs  will  be  found  in  the  same  situations  as  the 
adults.  They  resemble  the  adults  quite  closely  in  form, 
but  are  smaller,  and  lack  fully  developed  wings. 

Collect  nymphs  in  all  stages. 

Collect  adults  of  different  species  for  comparison. 

Collect  for  dissection  a  few  of  the  very  largest  speci- 
mens obtainable,  of  any  species. 

Study  in  the  field  (for  the  Carolina  locust)  :  — 

1.  Its  protective  coloring. 

2.  Its  several  methods  of  locomotion. 


THE   GRASSHOPPER.  49 

3.  The  sounds  (stridulatiori)  made  by  some  individuals 
(males)  while  on  the  wing. 

4.  Its  hours  of  activity. 

5.  Its  natural  enemies. 

6.  The  effect  of  temperature  upon  its  activity.     Go  out 
some  frosty  morning  for  this  purpose. 

Place  a  live  specimen  under  a  tumbler,  and  study :  — 

1.  Its  respiratory  movements.      Observe   the  opening 
and  closing  of  two  lips  that  guard  the  entrance  to  a  large 
spiracle  just  above  the  base  of  one  of  the  middle  legs. 
Find  other  active  spiracles. 

2.  The  size  and  arrangement  of  its  legs  in  relation  to 
the  locomotor  habits  of  the  animal;  which  legs  are  most 
serviceable  in  walking,  in  leaping. 

3.  Its  manner  of  feeding.     Place  some  fresh  leaves  of 
clover  or  of  lettuce  under  the  tumbler  with  the  insect, 
and  watch  it  eat.     If  kept  without  food  for  half  a  day,  it 
will  eat  greedily. 

Liberate  an  active  specimen  in  a  warm  room,  and 
measure  its  longest  leap  in  number  of  times  its  own 
length. 

External  Anatomy.  —  Observe  the  relative  development 
of  head,  thorax,  and  abdomen. 

Examine,  as  before,  the  upper  parts  of  the  head,  eyes, 
ocelli,  and  antennae. 

I.  Mouth  Parts.  —  Study  the  mouth  parts  with  especial 
care ;  for  in  the  grasshopper  all  the  typical  mouth  parts 
of  an  insect  are  present  and  well  developed.  Find,  pro- 
ceeding from  the  front :  — 

1.  A  large,  two-lobed  labrum. 

2.  A  pair  of  toothed,  horny  mandibles,  covered  by  the 
labrum. 

3.  A  pair  of  maxilla,  jointed,  compound  organs,  each 
bearing  at  its  summit  three  appendages. 

NEED.  ZOOL.  — 4 


50  INSECTS. 

(a)  The  lacinia  (or  blade),  the  innermost  part,  the  part 
used  in  biting. 

(5)  The  galea,  spoon-shaped,  and  covering  the  lacinia 
externally. 

(c)  The  maxillary  palpus,  a  jointed,  tactile  organ  out- 
side. Count  its  joints. 

4.  A  two-lobed  labium  (or  lower  lip),  bearing  below  a 
pair  of  jointed  labial  palpi. 

5.  A  fleshy  tongue,  between  and  below  the  maxillae. 
Separate  these  mouth  parts,  and  examine  each  with  a 

lens.     Draw. 

II.  Thoracic  Segments.  —  Note  the  relative  size  of  the 
three  thoracic  segments.    Note  their  peculiarities  of  form, 
color,  and  surface  markings.     Locate  their  spiracles. 

III.  Wings.  —  Study  the  wings.     Seize  the  fore  wing 
by  its  costal   margin,  draw  it  forward,  and  fasten  it  at 
right  angles   to  the   body.     Then  in   the  same   manner 
draw  the   hind  wing  forward.     Note   how  it   is  folded. 
Compare  the  two  wings  in  form,  color,  size,  texture,  posi- 
tion, and  use.       The  dry,  horny   fore   wings   of    grass- 
hoppers are  called  tegmina.    Find  in  one  of  the  tegmina 
five    principal   veins,  —  costal,    subcostal,    median,    sub- 
median,   and  internal,  —  starting  outward  from  its  base. 
Observe  that  each  of  the  tegmina  is  marked  off  into  three 
areas, — the    costal,    median,    and    internal   areas.       The 
median  area  lies   between  the  subcostal  and   submedian 
veins;  the  costal  area,  anterior  to  the  median;  the  internal 
area,  posterior  to  it. 

Make  an  enlarged  and  accurate  drawing  of  a  tegmen, 
naming  all  the  veins  and  areas  upon  the  drawing. 

It  is  by  rubbing  together  the  lower  surfaces  of  the  teg- 
mina, and  the  upper  surface  of  the  costal  vein  of  the 
hind  wing,  that  the  males  of  this  species  produce  the 
sounds  called  stridulation,  in  flight.  Examine  these  sur- 
faces with  a  lens. 


THE   GRASSHOPPER.  51 

IV.  Legs.  —  Compare  the  first  and  second  pairs  of  legs 
with  the  third  pair,  in  color  and  surface  markings,  posi- 
tion, size,  and  use. 

Find  in  one  of  the  hind  legs  the  usual  segments,  — 
coxa,  trochanter,  femur,  tibia,  and  tarsus.  Note  :  — 

1.  The  large    club-shaped  femur.     Within   it   are  the 
powerful  muscles  used  in  leaping. 

2.  The    double    row    of    spines    on    the    sides    of    the 
tibia. 

3.  The  two  pairs  of  spurs  at  its  lower  end. 

4.  The   tarsus.      Examine   its   lower   surface   and   the 
hooks  at  its  tip. 

What  is  the  advantage  of  all  these  spines  and  hooks 
and  pads  ? 

Make  an  enlarged  drawing  (lateral  view)  of  one  of  the 
hind  legs  in  its  natural  resting  position,  naming  all  the 
parts  in  the  drawing. 

V.  The  Abdomen.  —  Count  the  segments  of  the  abdo- 
men as  seen  on  the  ventral  surface.     In  the  female  there 
are  eight,  and  in  the  male  nine.      The  abdomen  of  the 
female  terminates  in  an  ovipositor,  having  four  subequal 
points,  which  are  used  for  making  holes  in  the  ground 
for  the  reception  of  eggs.     The  four  points  are  repeat- 
edly pressed  together,  »pushed  into  the  ground,  and  there 
separated,  thus  pressing  the  earth  aside,  until  a  hole  is 
made  of  sufficient  depth,  when  the  eggs  are  deposited 
in  the  bottom.     An  elongated,  bilobed,  subgenital  plate 
at   the    ventral   surface  terminates  the  abdomen  of   the 
male. 

Observe  on  either  side  of  the  abdomen  a  longitudinal 
groove,  and  just  above  it  a  row  of  evident  spiracles. 

Observe  on  either  side  of  the  first  abdominal  segment  a 
semicircular  depression,  across  which  is  stretched  a  thin 
membrane.  This  is  called  the  tympanum,  and  is  supposed 
to  be  an  organ  of  hearing. 


52  INSECTS. 

Internal  Anatomy. —  Select  for  dissection  large  female 
grasshoppers,  the  larger  the  better.  On  the  Western 
plains  the  lubber  grasshopper  (Brachystola  magna),  and 
in  the  South  the  American  locust  (Schistocera  americana), 
will  be  obtainable,  and  will  serve  better  than  the  Carolina 
locust,  because  larger.  Have  specimens  freshly  killed  in 
the  cyanide  bottle. 

Do  not  begin  a  dissection  when  tired  or  nervous,  for 
eager  eyes  and  steady  nerves  are  necessary  to  success. 
Should  you  injure  some  one  organ  in  the  first  dissection, 
and  so  not  see  it  satisfactorily,  make  a  special  dissection 
to  find  it  in  another  specimen. 

Dissect  the  grasshopper  on  a  shingle  or  bit  of  board.1 
Place  it  back  uppermost,  and  head  from  you.  Spread  the 
wings,  and  pin  them  so.  Pin  the  last  segment  of  the 
abdomen  firmly  to  the  shingle.  With  sharp,  fine-pointed 
scissors,  make  a  shallow  cut  through  the  skin  of  the  abdo- 
men, from  the  ovipositor  forward,  keeping  some  distance 
to  the  left  of  the  median  line,  and  continue  the  cut  for- 
ward to  the  head  along  the  thorax  at  the  bases  of  the 
left  wings.  Then  with  forceps  gently  lift  the  right-hand 
edge  of  the  skin  above  the  abdomen,  and  look  beneath  it 
for  a  delicate,  whitish  vessel,  the  dorsal  vessel,  sometimes 
improperly  called  the  heart.  It  is  but  a  series  of  thin- 
walled  chambers,  into  which  the  blood  flows  through 
lateral  valves,  and  through  which  it  progresses  forward 
toward  the  head.  You  will  find  the  colorless  blood  bath- 
ing all  the  internal  organs.  A  microscopic  examination 
of  a  drop  of  it  will  reveal  its  white  corpuscles.  The 
dorsal  vessel  lies  close  to  the  roof  of  the  abdomen,  is  very 
liable  to  be  injured  in  the  opening  of  the  skin,  and  may 
sometimes  be  best  approached  by  a  dissection  from  the 
ventral  side.  Make  a  second  cut  similar  to  the  first, 
on  the  right  of  the  median  dorsal  line  of  the  body,  and 
1  Or  under  water,  if  preferred.  See  Appendix,  p.  283. 


THE   GRASSHOPPER.  53 

carefully  remove  the  roof  of  skin  included  between  the 
two  cuts.  Observe  the  thin,  longitudinal  muscle  fibers 
lining  the  roof  of  the  abdomen,  and  the  heavy  wing  mus- 
cles completely  filling  the  upper  part  of  the  thorax. 

I.  Tracheae  and  Ovaries.  —  Press  the  body  walls  lightly 
outward,  and  observe  the  numerous  white  air  tubes 
(tracheae).  Observe  that  the  tracheae  arise  from  the  spira- 
cles; that  their  larger  branches  unite  to  form  longitudinal 
passageways  along  the  sides  of  the  body;  and  that  the 
smaller  branches  ramify  throughout  the  entire  body,  con- 
veying air  to  all  parts.  Observe  a  loose,  whitish  mass  of 
these  smaller  branches  now  lying  exposed  in  the  abdomen, 
on  top  of  other  organs.  Place  a  small  portion  of  this  mass 
in  a  drop  of  water  on  a  slide.  Cover  it  lightly  with  a 
cover  slip,  and  examine  with  low  power  to  make  out :  — 

1.  The  branching  tracheal  tubes. 

2.  The  spiral  elastic  fiber  which  is  coiled  around  the 
wall  of  each  to  keep  it  open. 

Two  large  and  conspicuous  yellow  egg  masses  are  usually 
present  in  the  abdomen  of  the  female.  These  contain 
many  cylindrical  eggs,  piled  like  cord  wood  in  ricks  or 
in  tierlike  masses.  Separate  the  two  masses  by  pushing 
a  dull  instrument  between  them  on  the  median  line.  Ob- 
serve that  each  egg  mass  (ovary)  has  a  white  tube  (an 
oviduct)  leading  down  to  the  ovipositor.  Carefully  re- 
move the  egg  masses,  and  pin  back  securely  both  free 
edges  of  the  skin. 

II.  Organs  of  Digestion.  —  Study  the  digestive  system. 
The  alimentary  canal,  dark-colored  and  conspicuous,  will  be 
easily  seen  extending  through  the  body  lengthwise.  Be- 
ginning at  the  mouth,  make  out  the  parts  of  it,  together 
with  the  accessory  organs,  as  follows :  — 

1.  The  mouth  opens  into  an  esophagus  which  extends 
upward  into  the  head,  then  backward  into  the  thorax, 
bending  at  right  angles. 


54  INSECTS. 

2.  The  esophagus  dilates  posteriorly  to  form  the  inglu- 
vies  (or  crop),  a  large  food  reservoir,  and  an  important 
organ  of  digestion.     Its  interior  surface  is  furnished  with 
many  ridges  and  conical  processes  which  aid  in  commi- 
nuting the  food. 

3.  On  the  sides  of  the  esophagus  lie  the  delicate,  white, 
branching  salivary  glands.     These  communicate  with  the 
mouth  by  means  of  two  salivary  ducts  that  run  forward 
along  the  sides  of  the  esophagus. 

4.  The  proventriculus  (or  gizzard)  is  the  portion  of  the 
food  canal  next  succeeding  the  crop.     Between  the  two 
there  is  no  separating  constriction,  such  as  there  is  in  many 
other   insects.      The  proventriculus  has  thick,  muscular 
walls,  also  armed  within  for  the  comminution  of  food. 

5.  A  circle  of  conspicuous  appendages  (the  gastric  cceca) 
marks  the  posterior  boundary  of  the  proventriculus.    These 
are  spindle-shaped  appendages  extending  lengthwise  of  the 
food  canal,  and  attached  laterally,  having  both  ends  free. 
Each  is,  in  fact,  composed  of  two  cone-shaped  glands  placed 
base  to  base.     The  function  of  these  glands  is  to  secrete  a 
digestive  fluid. 

6.  Posterior  to  these  is  the  ventriculus  (or  stomach), 
hardly  distinguished  by  its  external  appearance  in  the 
grasshopper    from   adjacent   portions   of    the   alimentary 
canal. 

7.  At  its  posterior  end  arises  a  circle  of  long,  slender, 
inconspicuous  tubes  (the  Malpighian  vessels')  which  float 
free  in  the  body  cavity.     Their  function  is  urinary. 

8.  The  remainder  of  the  alimentary  canal  is  the  intestine. 
A  study  of  the  parts  here  disclosed  will  give  a  general 
idea  of  the  digestive  system  for  all  insects. 

Let  us  now  review  the  digestive  process.  The  food  is 
first  masticated  by  the  mandibles  and  by  the  lacinise  of  the 
maxillae  in  the  mouth,  is  acted  upon  by  the  secretions  of 
the  salivary  glands  as  it  passes  from  the  mouth  into  the 


THE   GRASSHOPPER.  55 

esophagus,  is  further  comminuted  and  in  part  digested  in 
the  crop  and  gizzard,  is  acted  upon  by  the  secretions  of 
the  gastric  caeca  as  it  passes  into  the  stomach,  where  diges- 
tion is  in  the  main  completed.  The  digested  food  passes 
out  through  the  walls  of  the  alimentary  canal  directly  into 
the  blood,  which  bathes  all  the  organs,  and  supplies  them 
with  constructive  material  thus  obtained  from  the  food. 
The  Malpighian  vessels  reach  out  into  the  blood  and 
absorb  from  it  noxious  waste  products  of  the  body,  which 
they  pass  along  out  through  the  intestine,  together  with 
the  indigestible  portion  of  the  food.  The  blood  gets 
oxygen,  necessary  for  both  constructive  and  destructive 
processes,  by  absorption  of  it  (endosmosis)  through  the 
tracheal  walls. 

III.  Nervous  System.  —  Remove  carefully  the  alimen- 
tary canal  and  its  appendages,  and  look  on  the  floor  of  the 
body  cavity  for  a  double  nerve  cord  extending  the  length 
of  the  body,  the  two  threads  of  it  connecting  on  nearly 
every  segment  with  a  double  ganglion  (a  little,  roundish 
mass  of  nervous  matter).  Observe  the  nerve  fibers  that 
radiate  from  each  ganglion.  These  go  to  supply  nerve 
force  to  all  parts  of  the  body,  and  to  supply  nervous  com- 
munication between  the  parts.  Trace  the  double  nerve 
cord  to  the  head;  then  turn  the  head  on  one  side,  and  pin 
it  firmly  there  through  the  front ;  cut  away  the  upper  parts 
until  you  discover  a  large  ganglion  situated  above  the  be- 
ginning of  the  esophagus,  the  cephalic  ganglion  (or  brain) . 
Observe  that  the  double  nerve  cord  begins  here  and  passes 
one  thread  around  each  side  of  the  esophagus  to  the  first 
thoracic  ganglion,  and  thence  to  the  others  of  the  system. 

Development.  —  The  development  of  the  Carolina  locust 
may  easily  be  traced,  if  the  specimens  of  nymphs  collected 
alive  are  placed  under  a  bell  jar  or  glass  dish,  kept  sup- 
plied with  fresh  clover  or  lettuce  leaves  and  water,  and 


56  INSECTS. 

watched.  With  no  more  apparatus  than  this,  specimens 
may  be  reared  from  the  egg  to  the  adult  condition.  Since 
this  would  require  much  time,  it  is  better  for  the  student 
to  get  developing  nymphs  in  as  many  sizes  as  possible,  and 
keep  them  long  enough  to  see  different  molts  gone  through 
with  by  different  individuals. 

Study  the  molting  process,  and  by  careful  observations 
get  at  the  answers  to  such  questions  as  the  following  :  — 

1.  Has  the  nymph,  when  first  hatched  from  the  egg, 
any  wings?     (Use  lens  in  determining.) 

2.  Where  does  the  nymph  skin  split  open  when  molt- 
ing occurs? 

3.  What  part  of  the  insect  comes  out  first? 

4.  Does  the  insect  have  any  difficulty  in  withdrawing 
any  parts  of  its  body  from  the  old  skin? 

5.  What  signs  that  molting  is  about  to  occur  are  dis- 
coverable in  the  appearance  or  actions  of  the  nymph? 

6  What  is  the  condition  of  the  insect's  exterior  before 
molting,  and  after? 

7.  What  organs  are  relatively  best  developed  and  what 
least  developed  in  early  stages,  and  for  what  organs  has 
the  newly  hatched  nymph  most  use  ? 

Life-History  Box.  —  Make  a  life-history  box  for  the 
Carolina  locust.  Get  a  neatly  lined  cigar  box,  and  mount l 
in  it  a  complete  series  of  specimens  from  egg  to  adult, 
inclusive.  The  specimens  should  all  be  mounted  on  pins 
stuck  in  thin  sections  of  cork  glued  fast  to  the  bottom 
of  the  box.  The  eggs  will  need  to  be  fastened  with 
mucilage  to  a  bit  of  paper,  through  which  the  pin  may 
be  thrust.  The  very  smallest  nymphs  will  need  to  be 
mounted  in  the  same  way.  The  larger  ones  will  have  the 
pins  stuck  vertically  through  the  middle  of  the  thorax.  In 
addition  to  nymphs  of  all  sizes,  exuviae  should  be  mounted 

i  See  note  on  mounting  insects,  in  Appendix,  p.  283. 


THE   SQUASH  BUG.  57 

separately.  One  or  two  nymphs  should  also  be  taken  while 
emerging  from  the  exuviae,  killed  in  the  cyanide  bottle,  and 
mounted  in  that  condition.  Then  two  adults  of  each  sex 
should  be  included,  —  one  of  each  mounted  with  its  wings 
closed ;  another,  with  wings  fully  spread.  All  the  speci- 
mens should  stand  two  thirds  of  the  way  up  the  pins.  Such 
a  box  is  easily  prepared.  It  tells  the  story  of  the  develop- 
ment of  the  species.  If  the  Carolina  locust  is  not  so 
easily  obtained  in  full  series  as  another  species,  any  other 
grasshopper  will  do  as  well. 

All  the  grasshoppers  and  locusts  belong  to  the  group 
Orthoptera  (or  straight- winged  insects). 

Other  Orthoptera  are  crickets,  katydids,  walking  sticks, 
mantes,  cockroaches,  etc.  Some  of  these  should  be  stud- 
ied, and  compared  with  the  grasshoppers  in  size,  in  relative 
development  of  organs,  in  relative  powers  of  locomotion,  in 
food,  in  habits,  in  instincts,  and  in  economic  importance. 
A  good  general  idea  of  the  group  will  thus  be  obtained. 

THE  SQUASH  BUG. 

(Anasa  tristis.) 

Haunts  and  Habits.  —  This  insect  is  an  annoying  pest 
of  the  kitchen  garden.  Adults,  young,  and  eggs  may  all 
be  collected  from  the  same  vines  of  squash, 
cucumber,  or  pumpkin.  The  adults  are  black- 
ish brown  above,  and  dirty  yellow  beneath. 
The  nymphs  are  smaller,  and  relatively  shorter 
and  more  rounded,  than  the  adults.  The  eggs 
are  laid  in  little  clusters  on  the  young  leaves. 

No  net  will  be  needed  for  collecting  these  SQUASH  BuG' 
bugs.  They  may  be  pushed  directly  into  the  cyanide 
bottle.  While  collecting,  observe  the  following  points. 


58  INSECTS. 

1.  Their  position  on  the  leaf  while  feeding. 

2.  Their  manner  of  feeding. 

3.  The  effect  of  their  operations  on  the  leaf. 

4.  Under  what  conditions  one  leaf  is  ordinarily  deserted 
for  another. 

Study  of  a  Live  Specimen.  —  Study  the  adult. 

Examine  the  head  with  a  lens.  Note  the  position  of 
its  parts.  Find  eyes,  ocelli,  and  antennae. 

Observe  that  the  mouth  parts  are  modified  into  a  jointed 
proboscis  (the  rostrum).  Count  its  joints.  Note  its  posi- 
tion. At  the  base  of  the  rostrum  above  is  the  rudimen- 
tary labrum.  Mandibles  and  maxillae  are  represented  by 
two  pairs  of  bristles  within  the  sheath  of  the  rostrum. 
The  sheath  itself  is  supposed  to  be  the  modified  labium 
consolidated  with  its  palpi.  The  whole  rostrum  is  well 
adapted  to  making  punctures,  and  to  sucking  up  through 
them  the  juices  of  plants. 

Observe  for  the  thorax  its  shape  and  the  relative  de- 
velopment of  its  segments. 

On  the  mesosternum  at  either  side,  near  each  middle 
coxa,  find  a  small  pore  (an  osteole)  surrounded  by  a  small 
granular  space  (the  evaporating  surface).  From  these 
osteoles  is  exuded  the  fluid  Avhich  gives  the  squash  bug  its 
peculiar  odor.  This  odor  is  protective,  because  it  makes 
the  bug  a  less  dainty  morsel  of  food  for  other  animals. 

Examine  the  legs.  For  what  kind  of  locomotion  are 
they  adapted?  Find  coxa,  trochanter,  femur,  tibia,  and 
tarsus.  How  many  joints  in  the  tarsus  ? 

Examine  the  wings.  Observe  carefully  the  difference 
between  inner  and  outer  halves  of  the  fore  wing,  the  former 
thickened  and  horny,  the  latter  membranous  and  traversed 
by  numerous  veins.  Compare  fore  and  hind  wings  in 
form,  size,  texture,  and  position.  Draw  the  wings  of  one 
side  (enlarged). 


THE  TWO-YEAR   CICADA, 


59 


Make  a  life-history  box  for  the  squash  bug. 

The  squash  bug  is  a  representative  of  the  group  Hemip- 
tera  (or  half -winged  insects). 

Other  Hemiptera.  —  All  the  "  bugs,"  properly  so  called, 
belong  in  the  order  Hemiptera,  together  with  plant  lice, 
bark  lice,  tree  hoppers,  cicadas,  etc.  But  two  other  types 
will  be  selected  here  for  study. 


THE  TWO-YEAR  CICADA  OR  DOGDAY  HARVEST  FLY. 

(Cicada  tibicen.) 

Haunts. — This  is  the  insect  commonly  but  improperly 
called  "locust."  It  may  be  found  about  shade  trees  in 
late  summer  and  autumn.  Its  col- 
ors are  black  and  green,  powdered 
with  white  beneath.  The  adults 
may  be  followed  by  ear  to  their 
resting  places  •  on  the  boughs  of 
shade  trees,  their  shrill  cries  being 
the  most  prominent  and  the  best 
known  of  the  various  insect  sounds 
of  late  summer  and  of  autumn. 
The  nymphs  are  seldom  seen ;  but 
the  exuvise  which  they  shed  at 
their  last  molt  are  large,  and  con- 
spicuous objects  of  common  obser- 
vation. They  are  found  clinging 
to  weeds,  bushes,  trees,  or  fences  in  early  summer.  The 
eggs  are  laid  in  slits  made  in  the  twigs  of  trees.  When 
hatched,  the  young  drop  to  the  ground  and  bury  them- 
selves, and  feed  upon  the  juices  obtained  by  puncturing 
the  roots  of  trees.  Two  years  are  required  to  complete 
their  growth.  The  second  summer  following  hatching, 


TWO-YEAR  CICADA. 


60  INSECTS. 

the  nymph  comes  above  ground,  crawls  a  little  way  up  a 
convenient  reed  or  board,  fastens  its  feet  firmly,  and  is 
ready  to  transform.  The  skin  splits  down  the  back  of 
both  head  and  thorax ;  the  perfect  insect  steps  out,  rests 
awhile,  and  expands  and  dries  its  wings,  and  then  flies 
away  with  a  noisy  "whirr"  to  its  new  home  in  the  tree 
tops. 

Study  of  a  Live  Specimen.  —  Get  an  adult  specimen  for 
study,  and  observe  :  — 

1.  The  shape  of  its  body  as  a  whole. 

2.  The  point  where  the  rostrum  arises  from  the  head. 

3.  The  position  of  the  eyes  and  ocelli. 

4.  The  absence  of  any  neck,  and  the  consequent  ap- 
proximation of  cheeks  and  coxae  of  the  anterior  pair  of 
legs. 

5.  The  markings  on  the  top  of  the  thorax. 

6.  The  sloping  position  of  the  wings. 

7.  The  structure  of  the  fore  wings, — that  they  are  not 
half  horny  and  half  membranous,  but  wholly  membranous. 

8.  The   musical   organs   at   the   base   of   the   abdomen 
above  (found  only  in  the  males), — two  ribbed  and  plaited 
parchment  bags  situated  in  depressions,  one  on  either  side 
of  the  median  dorsal  line,  provided  with  powerful  muscles 
for  driving  air  against  the  fluted  surfaces.     This  sets  up 
vibrations,  producing  sounds,  which  vary  in  different  indi- 
viduals with  the  proximity  and  form  of  the  spaces  and 
ribs. 

If  the  large  rostrum  of  the  cicada  be  dissected,  the  two 
pairs  of  punctorial  bristles  will  be  easily  found  within  the 
sheath. 

Compare  adults  of  cicada  and  squash  bug  with  refer- 
ence to  shape  of  head  ;  place  of  origin  of  rostrum ;  length 
of  neck ;  structure,  position,  and  method  of  folding,  of 
wings. 


THE   BACK-SWIMMER.  61 

Get  an  exuvia  of  a  cicada,  and  study  it  carefully.  Do 
not  fail  to  note  how  completely 
the  hard,  external  skeleton, 
together  with  its  internal  pro- 
jections, is  shed.  Compare  it 
with  the  adult  in  form  and  rela- 
tive development  of  locomotive 

organs.  NYMPH  OF  HARVEST  FLY. 


THE   BACK-SWIMMER. 

(Notonecta.) 

Haunts  and  Habits.  —  This  insect  is  abundant  in  the 
pools  of  brooks  and  in  ponds.  It  is  a  little  over  half  an 
inch  in  length.  It  may  readily  be  recognized  by  its  in- 
verted position  in  the  water.  It  swims  on  its  back,  and 
rests  with  its  wing  tips  just  touch- 
ing the  surface  of  the  water,  and  its 
long  hind  legs  poised  forward  and  ex- 
tended on  either  side.  When  startled, 
it  darts  away  toward  the  bottom  :  but  it 
BACK-SWIMMER,  NO-  wiU  rise  again  immediately  when  it  stops 

tonecta    (slightly     swimming-,  unless  it  holds  to  some  sub- 
enlarged).  ,      ,  , 

merged  object;  for  its  body,  together 
with  the  air  inclosed  beneath  its  wings  and  between  its 
thoracic  segments,  is  much  lighter  than  the  water. 

Back-swimmers  are  easily  taken  in  a  net.  All  stages 
will  be  found  together.  They  may  be  kept  at  home  in  a 
bowl  of  water,  and  their  habits  studied.  Care  should 
be  exercised  in  handling  them,  for  they  will  sometimes 
inflict  wounds  with  their  sharp  and  strong  rostrum. 
When  it  is  necessary  to  take  one  alive  with  the  fingers,  it 
may  safely  be  picked  up  by  the  sides  of  the  body.  Back- 
ris  present  many  interesting  adaptations  to  aquatic 


62  INSECTS. 

life,  and  are  especially  worthy  to  be  studied  alive.     Study 
them  so,  either  at  home  or  in  their  native  pools. 

Study  of  a  Live  Specimen.  —  Observe  :  — 

1.  The  boat-shaped  body. 

2.  The  oarlike  position  and  action  of  the  long  hind  legs. 

3.  The  winy  tips  reaching  the  surface,  and  admitting 
beneath  the  wings  a  supply  of  air,  which  may  be  breathed 
when  the  insect  is  at  the  bottom. 

4.  The  thin  layer  of  air  surrounding  the  thorax  (easily 
seen  at  the  joints  when  the  body  is  bended). 

Place  one  on  a  dry  surface :  see  it  walk. 

Throw  an  adult  up  into  the  air :  see  it  fly.  It  can 
arise  in  flight  direct  from  the  water. 

Study  the  external  features  in  order,  as  outlined  for 
other  insects,  noting  especially  :  — 

1.  The  junction  of  the  head  with  the  prothorax. 

2.  The  position  of  the  antennce. 

3.  The  shape,  size,  and  position  of  the  eyes. 

4.  The  absence  of  ocelli. 

5.  The  sharp,  lateral  edges  of  thorax  and  abdomen. 

6.  The  hairiness  of  parts. 

7.  The  form,  size,  and  position  of  the  legs. 

8.  The  structure  of  the  tarsi  (use  a  lens). 

9.  The  structure  and  position  of  the  wings. 

10.  The  relation  between  the  spiracles  and  the  air 
inclosed  beneath  the  wings. 

Then  answer  these  questions  :  — 

1.  What  advantages  are  secured  to  the  back-swimmer 
by  the  peculiar  shape  of  its  body? 

2.  Need  locomotive  organs  be  more  complex  for  pro- 
gression in  the  water,  or  on  the  land?     Why? 

3.  What   other   devices   for  aquatic   respiration   have 
you  studied,  and  what  points  had  each  in  common  with 
the  respiratory  method  of  this  insect? 


THE   BUMBLEBEE.  63 


THE  BUMBLEBEE. 

Haunts  and  Habits.  — A  field  of  blossoming  clover,  or  a 
fence  row  grown  up  with  bergamot  or  other  mints,  is  a  good 
place  to  observe  something  of  the  habits  of  the  bumble- 
bee, —  to  learn  something  of  its  part  in  the  economy  of 
nature,  which  may  not  be  so 
well  learned  anywhere  else.  A 
half  hour  spent  in  studying  the 
bumblebee  among  the  flowers 
from  which  it  feeds  may  be 
made  most  profitable.  It  will 
not  behave  normally  in  confine- 

.„  BUMBLEBEE  (slightly  enlarged) . 

ment;    but   it   will   not   resent 

close  scrutiny  while  free,  and  feeding  from  its  favorite 
flowers,  if  it  be  approached  quietly.  Watch  a  bumblebee 
on  a  head  of  red  clover.  See  how  roughly  it  tramples 
over  the  tops  of  the  corollas.  Observe  that  it  collects 
two  products  of  the  flowers  :  — 

1.  Nectar,  from  the  bottom  of  the  corolla  tubes,  which 
it  stops  momentarily  to  sip  as  it  passes  over.     Note  the 
position  and  shape  of  the  organ  used  in  sucking  up  the 
nectar. 

2.  Pollen,  the  yellow  dust  which  falls  from  the  anthers 
of  the  flowers  when  they  are  shaken.     This  is  collected 
into  the  pollen  baskets  on  the  hind  legs.     The  yellowish 
lumps  of  pollen  will  be  conspicuous  on  some  of  the  in- 
dividuals seen. 

Note  whether  the  bumblebee  visits  one  species  of 
flower,  or  several,  in  a  single  trip  out  from  the  nest.  Fol- 
low one  from  flower  to  flower,  until  you  ascertain  what  is 
its  habit  in  respect  to  this. 

What  other  insects  have  you  studied  that  feed  upon 
red  clover  ?  The  life  of  quite  a  number  of  very  common 


64  INSECTS. 

insects  and  other  animals  is  more  or  less  dependent  on 
red  clover.  The  bumblebee  is  an  animal  011  which  the 
life  of  red  clover  is  more  or  less  dependent.  The  bumble- 
bee gives  value  received  for  all  the  nectar  and  pollen  it 
takes  from  the  clover. 

Clover  must  produce  seed,  or  soon  die  out.  The  flower 
must  be  fertilized  in  order  to  produce  seed.  The  floAver 
can  be  fertilized  only  by  means  of  pollen  carried  to  its 
pistil  from  the  anthers  of  another  flower.  The  bumble- 
bee is  the  carrier  of  the  pollen.  Its  rough-and-tumble 
manner  of  feeding  is  well  adapted  to  dislodging  the  pol- 
len, much  of  which  falls  on  its  body,  and  is  scattered  over 
the  flowers  next  visited,  securing  their  fertilization.  Thus 
the  insect's  wasteful  method  of  gathering  the  pollen  is  seen 
to  be  exactly  adapted  to  the  requirements  of  the  plant. 

Spray  a  bumblebee  with  water,  and  note  the  effect  on 
its  power  of  flight.  What  becomes  of  one  when  caught 
out  in  a  shower? 

Compare  a  bumblebee  with  a  butterfly  in  :  — 

1.  Speed  and  directness  of  flight. 

2.  Relative  size  of  body  and  wings. 

3.  Rapidity  of  wing  strokes. 

Catch  a  bumblebee  in  a  net,  and  observe  that  the  pitch 
of  its  humming  when  captive  is  higher  by  several  tones 
than  when  free.  Why?  Collect  with  net  and  cyanide 
bottle  a  few  large  specimens  for  use  in  studying  its 
anatomy. 

External  Anatomy  of  the  Adult.  —  Study  carefully  to 
make  out  the  parts,  as  mentioned  already  for  other  insects. 
The  same  parts  are  present,  and  in  the  same  relative  *posi- 
tions,  but  modified  to  meet  the  needs  of  an  animal  of  dif- 
ferent life  and  different  habits. 

I.  The  Head.  —  Make  a  drawing  of  the  head  as  seen 
from  above,  showing  accurately  eyes,  ocelli,  and  antennae. 


THE   BUMBLEBEE.  65 

Study  the  mouth  parts,  observing  another  modification 
and  arrangement  of  them,  as  follows  :  — 

1.  A  short,  firm  labrum. 

2.  A  pair  of  strong,  horny,  biting  mandibles. 

3.  A  proboscis  (or  sucking  organ),  bent  backward  at 
the  middle,  and  resting  against  the  lower  surface  of  the 
head  and  thorax  when  not  in  use,  and  composed  of  — 

(a)  A  long,  hairy,  tubular  ligula  (or  central  piece)  of 
the  labium  (centrally). 

(6)  Two  margined  blades  of  the  maxilla  (above). 

(<?)  Two  thin,  narrow,  elongated  labial  palpi  (below). 
Separate,  and  examine  these  parts  with  a  lens.  Draw. 

II.  Wings  and  Legs.  —  Compare  fore  and  hind  wings 
in  form,  size,  and  position. 

Draw  the  fore  wing  forward  by  its  costal  margin,  and 
observe  that  the  hind  one  moves  with  it.  Find  the  little 
hooks  (Jiamuli)  which  hold  the  two  together,  securing  their 
unity  of  action. 

Find  coxa,  trochanter,  femur,  tibia,  and  tarsus  in  one 
leg  of  each  pair.  How  many  segments  in  the  tarsus  ? 
Which  segment  of  the  tarsus  is  largest?  On  which  seg- 
ment of  the  hindmost  legs  are  the  pollen  baskets  ?  Ob- 
serve with  a  lens  the  surfaces  to  which  the  pollen  masses 
adhere,  and  the  means  by  which  they  are  protected  in 
position.  Make  a  detailed  drawing  of  a  hind  leg. 

III.  Thorax  and  Abdomen.  —  Study  the  attachments  of 
both  wings  and  legs  of  the  hindmost  pair,  to  ascertain 
the  posterior  boundary  of  the  thorax  and  the  beginning 
of  the  abdomen.     Scrape  off  the  hairs  from  the  top  of 
the  thorax,  and  observe  that  the  metathorax  is  a  narrow 
segment  (antero-posteriorly) ;  and  a  wider  segment  with- 
out appendages,  the  first  abdominal  segment,  is  solidly 
welded  to  it.     The  second  segment  of  the  abdomen  is  but 
a  short  and  narrow  stalk-like  ring,  attaching  the  ovate 
hinder  portion  of  the  abdomen.     Note  how  the  abdominal 

NEED.  ZOOL.  —  5 


66  INSECTS. 

segments  are  fitted  together,  and  IIOAV  great  freedom  of 
movement  is  secured  by  this  arrangement. 

At  the  posterior  end  of  the  abdomen  the  slender  point 
of  the  sting  may  be  seen  protruding.  Seize  it  with  for- 
ceps, and  pull  it  out  full  length.  Examine  with  low 
power.  Observe  that  it  is  hollow.  Find  the  poison 
glands  at  its  base.  The  sting  itself  makes  but  a  slight 
puncture,  which  would  hardly  be  noticed  by  the  larger 
animals  were  it  not  for  the  poison  poured  from  these 
glands  into  the  wound.  These,  together  with  the  great 
mobility  secured  by  the  structure  of  the  abdominal  seg- 
ments already  noticed,  make  it  a  formidable  weapon  of 
defense. 

Development.  —  The  development  of  the  bumblebee  may 
be  studied  throughout  in  a  single  well-stocked  nest.  Find 
a  bumblebees'  nest,  and  take  it  with  all  its  occupants. 
This  will  not  be  hard  to  do  in  summer  or  autumn.  Two 
methods  are  recommended  :  — 

1.  Having  located  the  nest,  go  out  for  it  after  sunset  or 
before   sunrise,  when   all  its  inhabitants  are  "indoors." 
Pour  chloroform  or  ether  into  the  nest.     Wait  a  moment 
for  the  bees  to  become  stupefied.     Then  take  up  the  nest 
entire,  keeping  the  chloroform  or  ether  at  hand,  ready  to 
be  dashed  into  the  nest  should  the  first  not  have  been 
sufficient.      But   little   of   it   will   be   required,    if   judi- 
ciously administered.    Care  should  be  exercised,  in  taking 
up  the  nest,  to  keep  it  in  good  shape  for  further  study 
of  its  structure  and  arrangement. 

2.  Another  method,  and  one  by  which  the  nest  may 
be  taken  during  the  day,  is  the  following :    Set  a  clean 
jug,  uncorked  and  with  some  water  in  it,  close  by  the 
nest.     Then  disturb  the  nest  (if  possible,  without  injuring 
its  structure),  and  retire  to  a  good  place  from  which  to 
watch.     The  bumblebees  will  attack  the  jug,  and  then 


THE   BUMBLEBEE.  67 

fly  into  it  and  get  into  the  water,  where  they  must 
remain.  When  all  have  gone  into  the  jug,  or  settled, 
disturb  the  nest  again.  Repeat  once  or  twice.  Then  all 
those  of  the  occupants  which  have  been  accustomed  to 
defend  the  nest  will  be  in  the  jug ;  and  the  few  remaining 
may  be  sprinkled  with  water,  and  picked  up  while  wet 
and  unable  to  fly,  or  caught  singly  in  a  net.  Obviously, 
the  entire  population  of  the  nest  will  not  be  caught  in 
this  way,  for  in  the  daytime  some  are  absent  foraging  in 
the  field.  Why  do  the  bumblebees  go  into  the  jug  ? 

Whatever  the  method  of  taking  the  nest,  all  its  occu- 
pants, as  well  as  the  nest  itself,  should  be  preserved  for 
future  study.  The  bumblebees  will  not  all  be  killed  at 
once  by  either  of  the  methods  suggested ;  but  they  may 
be  killed  in  alcohol  or  in  a  cyanide  bottle.  Those  taken 
in  a  jug  may  be  poured  out  with  the  water,  and  picked 
up  with  forceps  before  their  wings  have  dried. 

Study  the  adult  bumblebees  found  in  the  nest.  Find 
among  them  four  sorts  of  individuals  :  — 

1.  Numerous  small  ones,  built  for  activity, — the  workers 
(undeveloped  females). 

2.  Others  of  larger  size,  but  of  the  same  general  shape 
as  the  workers, — the  small  females. 

3.  Others  about  the  size  of  the  small  females,  or  some- 
what larger,  but  thicker,  clumsier,  and  more  hairy,  —  the 
males  (or  drones). 

4.  A   few  very  large  ones  (an   inch   long),  the  large 
females  (or  queens).     Until  late  in  the  season,  but  one 
of  these  will  be  found  in  each  nest. 

The  Nest.  —  Study  the  nest.     Note  :  — 

1.  The  location  of  it. 

2.  The  materials  used  in  its  construction. 

3.  The  structure  of  it. 
(a)  The  entrance  to  it. 


68  INSECTS. 

(6)  The  passageways  inside. 

(c)  Its  roof  :  will  it  shed  water  ? 

(d)  Its  floor. 

Within  the  nest  find  :  — 

1.  Yellowish  food  masses  of   mixed  pollen  and  honey, 
containing  — 

(a)  Small  clusters  of  white,  oblong,  or  elliptical  eggs. 

(5)  The  young  which  have  hatched  from  other  eggs, — 
white,  wormlike  creatures  of  various  sizes,  feeding  on  the 
pile  of  common  food. 

2.  Cells:  — 

(a)  Standing  open,  like  yellow  pots  (or  sometimes  filled 
and  closed),  containing  stored  honey. 

(6)  Capped  over,  and  containing  young. 

Within  the  nest  may  often  be  found  some  of  the  smaller 
insects,  which  are  parasites  of  the  bumblebee. 

Life  History.  —  Here  in  the  nest  is  disclosed  the  life 
history  of  the  bumblebee.  In  its  life  there  are  four 
stages. 

The  first  stage  is  the  egg. 

The  second  stage  is  the  wingless,  footless,  wormlike 
creature  which  we  call  the  larva.  The  larva  is  very 
small  when  it  emerges  from  the  egg,  but  it  grows  rapidly, 
for  its  sole  business  is  eating;  and.  when  it  is  fully  grown, 
it  spins  a  silken  cocoon  about  itself  and  enters  upon  the 
next  stage. 

The  third  stage  is  the  pupa.  In  the  pupa  stage  it 
remains  quietly  concealed  within  its  cocoon,  over  which 
the  workers  spread  a  thin  layer  of  wax,  making  a  cell 
out  of  it.  But  though  inactive,  very  important  changes 
are  taking  place  in  the  pupa;  for  when,  after  a  time,  it 
cuts  a  way  for  itself  through  the  top  of  its  cell,  it  comes 
forth,  not  the  wormlike  larva  which  went  in,  but  a  fully 
developed  bumblebee. 


THE   BUMBLEBEE.  69 

The  fourth  stage  is  the  imago,  the  adult  bumblebee. 

Select  one  of  the  largest  larvae  for  comparison  with  an 
imago.  Note  their  resemblances  and  their  differences  in 
structure. 

Open  a  number  of  the  cells,  and  examine  the  pupse  con- 
tained in  them.  Observe  the  gradual  evolution  of  the 
perfected  organs  of  the  imago.  Since  the  adult  partakes 
only  of  soft  food,  what  use  has  it  for  horny,  biting  man- 
dibles? 

Make  a  series  of  drawings  showing  the  life  history  of 
the  bumblebee.1 

Compare  the  transformations  of  the  bumblebee  with 
those  of  other  insects  studied.  When,  as  with  the  bumble- 
bee, there  are  four  stages,  — egg,  larva,  pupa,  and  imago,  — 
the  metamorphosis  is  said  to  be  complete.  When,  as  with 
the  grasshopper,  there  are  but  three  distinct  stages,  — egg, 
nymph,  and  the  perfect  insect,  —  with  no  pupal  or  resting 
stage  and  with  greater  likeness  to  the  adult  in  the  second 
stage,  the  metamorphosis  is  said  to  be  incomplete. 

The  History  of  a  Colony  of  bumblebees,  that  is,  of  a 
single  nest  and  its  occupants,  is  about  as  follows:  In  the 
spring  each  colony  is  founded  by  one  of  the  adult  females 
(or  queens)  which  alone  survive  the  winter.  Such  may 
be  seen  in  spring,  searching  the  meadows  over  for  a  place 
to  establish  a  nest.  When  proper  food  flowers  open,  each 
bumblebee  takes  possession  of  a  suitable  bunch  of  dried 
grass,  or  preferably  of  an  old  mouse  nest,  and  carries  into 
it  pollen  and  honey,  and  deposits  beside  the  food  a  few 
eggs.  All  the  work  of  providing  food  and  shelter,  and  of 
caring  for  this  first  brood,  is  done  by  the  queen.  The 
bees  of  this  first  brood  are  workers,  and  as  soon  as  they 
come  forth  from  their  pupal  cells  they  assume  most  of  the 

1  In  its  preparatory  stages,  the  insect  is  best  preserved  in  alcohol.  Eor 
a  suggestion  as  to  the  use  of  alcohol,  see  Appendix,  p.  277. 


70  INSECTS. 

duties  of  the  colony,  the  queen  continuing  to  lay  eggs, 
and  the  colony  growing  rapidly  in  numbers.  In  mid- 
summer a  brood  is  produced  of  small  females  and  males. 
The  broods  of  autumn  produce  only  large  females  (or 
queens),  and  only  these  survive  the  winter.  With  the 
coming  of  cold  weather,  all  others  perish. 

A  study  of  the  life  of  a  colony  explains  the  scarcity  of 
bumblebees  in  spring  and  early  summer.  Considered  in 
connection  with  their  fertilizing  agency  for  red  clover, 
it  explains  the  scarcity  of  seed  in  the  first  crop,  and  gives 
a  reason  why  the  second  crop  (the  late  crop)  is  always  the 
one  to  be  cut  for  seed. 

The  bumblebee  is  a  representative  of  the  group  Hyme- 
noptera  (or  membrane- winged  insects). 

Other  Hymenoptera  are  ants,  bees,  hornets,  wasps,  saw- 
flies,  gallflies,  etc.  The  three  mentioned  below  are  per- 
haps most  easily  procurable. 


THE  MUD  WASP   (OR  MUD  DAUBER). 

The  Mud  Wasp  is  a  solitary  hymenopter.     The  adult 
female  lives  and  labors  alone.     The  nests  may  be  found 

in  abundance,  adhering  to  the 
rafters  in  any  barn  loft  or  wood- 
house  attic,  and  are  too  familiar 
to  need  description. 

In  very  dry  weather  in  summer 
or  autumn,  the  adults  may  be  ob- 
served by  any  brookside,  at  the 
edge  of  the  water,  rolling  up  lit- 
OUTLINE  DRAWING  AND  DIA-      tie  balls  of  mud  and  flying  away 
GRAM  OF  A  WASP  (wings      with  them.     The  same  operation 

and  legs  of  right  side  not  _          ,  ,       .  t  n 

shown):  a, abdomen.  niay  often  be  seen  beside  a  well 


THE   MUD   WASP.  71 

where  water  has  been  spilled,  converting  the  dust  into 
mud.  The  peculiarities  in  the  flight  and  walk  of  the  wasp 
may  be  studied  in  such  places ;  and  specimens  for  study 
may  easily  be  taken  with  net  and  cyanide  bottle. 

Study  the  external  anatomy  of  the  adult,  noting  the 
development  of  all  the  parts,  and  especially  of  the  mouth 
parts  and  the  first  three  abdominal  segments. 

Study  of  a  Live  Specimen. —  Go  into  loft  or  attic,  or  other 
place  where  these  insects  are  building  their  nests  of  mud, 
and  watch  them  at  work.  They  will  not  sting  unless 
much  molested,  and  they  seem  to  have  little  objection  to 
being  watched.  Find  one  that  is  bringing  in  a  ball  of 
mud,  and  follow  it  to  its  nest.  Observe  :  — 

1.  How  the  ball  of  mud  is  carried. 

2.  How  it  is  deposited  and  worked  into  place. 

3.  The  peculiar  sound  the  wasp  makes  while  at  work, 
and  how  this  sound  is  made. 

4.  The  position  and  attachment  of  the  nest. 

5.  The  arrangement  of  its  cells. 

The  nest  may  easily  be  removed,  when  the  old  wasp  is 
absent,  by  pushing  a  knife  blade  under  it.  Study  the 
development  of  the  insect  as  shown  in  the  contents  of  the 
nest.  Examine  the  contents  of  all  the  cells.  Their  walls 
may  easily  be  cut  away  with  a  knife.  Find  :  — 

1.  A  cell  or  cells  unfinished,  and  containing  at  the  bot- 
tom a  single  egg. 

2.  Cells  uncapped,  and  partly  filled  with  little  spiders 
or  other  insects.     These  are  for  the  food  of  the  larva  that 
will  hatch  from  the  egg  in  the  bottom  of  each  cell.     Note 
the  condition  of  the  spiders,  —  not  dead,  but  paralyzed. 
A  number  of  days  elapse  after  they  are  put  into  the  cell 
before  the  larva  is  ready  to  eat  them,  and  they  would  de- 
compose if  killed  outright.     The  mother  wasp  stings  them 
in  such  a  manner,  that  they  are  only  paralyzed,  and  remain 


72  INSECTS. 

alive  but  inactive  till  wanted,  —  a  wonderfully  successful 
way  of  providing  her  offspring  with  "fresh  meat." 

3.  Cells  in  which  there  is  a  larva  feeding  on  the  spiders. 

4.  Cells  in  which  the  spiders  have  all  been  eaten  (save 
their  skins,  which  are  pushed  to  the  bottom  of  the  cell),  and 
in  each  of  which  there  is  a  larva  fully  grown,  or  perhaps 
transformed  into  a  pupa,  and  lying  quiescent  within  its 
thin  brown  pupa  skin. 

5.  Other  cells  showing  a  gradual  approximation  to  the 
adult  form. 

6.  A  cell  from  which  an  adult  has  just  emerged,  leav- 
ing pupa  skin  and  spider  skins  behind  in  the  cell. 

If  all  these  stages  be  not  found  in  a  single  nest,  several 
nests  should  be  examined.  Is  the  metamorphosis  of  the 
mud  was^omplete,  or  incomplete  ? 

THE  PAPER  WASP. 

The  Nest  consists  of  a  single  tier  of  gray,  papery  cells 
opening  downward,  and  attached  above  by  a  short  stalk  to 
the  eaves  of  a  building,  or  to  a  fence,  or  to  the  horizontal 
twig  of  a  small  bush.  This  description  ought  to  be  suf- 
ficient for  identifying  so  common  an  object.  The  adult 
wasps  are  always  found  upon  the  nest.  It  is  an  easy  mat- 
ter to  obtain  the  nest,  not  so  easy  to  get  all  the  wasps. 

Get  a  nest.  It  may  be  detached  with  a  long  pole. 
When  it  falls,  all  the  adult  wasps  leave  it.  Should  it  be 
a  large  and  heavy  nest,  located  high  above  a  hard  surface, 
some  soft  material,  as  straw,  should  be  placed  below  it  to 
break  its  fall ;  otherwise  many  of  the  cells  will  be  injured. 

Study  the  nest. 

I.  Construction.  —  Note  the  size,  shape,  and  position  of 
its  cells,  and  the  attachment  of  its  stalk.     Draw. 

II.  Material.  —  Examine  with  a  lens  the  paper  of   its 
cells.     It  is  made  from  fibers  of  wood  torn  from  boards 


THE    HONEYBEE.  73 

and  splintered  trees.  The  fibers  are  treated  with  salivary 
secretions,  and  reduced  to  a  pulp  in  the  mouth  of  the 
wasp.  The  pulp  is  then  fashioned  into  cell  wall,  where 
it  quickly  dries  and  hardens.  How  is  paper  made  from 
wood  in  paper  factories  ? 
III.  Contents  :- 

1.  Is  there  any  food  stored  in  it? 

2.  Where  is  the  egg  placed  in  the  empty  cell? 

3.  Is  the  larva  shut  up  with  a  store  of  food,  or  given 
food  as  it  needs  it? 

4.  At  what  stage  in  the  life  of  the  young  is  its  cell 
capped  over? 

Study  the  metamorphosis,  as  before  directed  for  the 
mud  wasp,  and  make  a  serial  drawing  showing  its  life 
history. 

THE  HONEYBEE. 

The  Honeybee  is  the  best  known  of  the  Hymenoptera. 
It  may  be  sought  wherever  there  are  flowers. 

Make  a  study  of  its  foraging  habits  and  of  its  structure, 
following  the  directions  given  for  the  bumblebee.  Then 
get  a  bee-keeper  friend  to  show  you  through  a  movable- 
frame  hive  in  his  apiary.  Ask  him  to  show  you  the  sol- 
itary female  called  queen,  and  the  clumsy  males  called 
drones.  Ask  him  about  the  swarming  habits.  If.  you 
have  not  this  privilege,  then  read  in  Quinby's  "  New  Bee 
Keeping,"  or  Professor  Cook's  "Manual  of  the  Apiary," 
the  chapters  on  the  natural  history  of  the  honeybee. 

The  Comb.  —  Examine  a  piece  of  empty  honeycomb, 
and  note  :  — 

1.  The  shape  and  arrangement  of  the  cells  on  one  side. 

2.  The  meeting,  at  their  bases,  of  cells  on  opposite  sides 
of  the  comb.      What  mechanical  and  economical  advan- 
tages do  you  discover  in  such  construction?     Does  this 


74  INSECTS. 

indicate    high   or    low   rank   in   the    insect's   instinctive 
endowments*? 

Compare  together  all  the  Hymenoptera  studied. 

Which  eat  animal  food?  Which  vegetable?  Which  both? 

Which  live  in  the  largest  colonies  ? 

Which  show  the  highest  instincts  in  the  construction  of 
their  nests  ?  In  the  care  of  their  young  ?  In  the  division 
of  labor  in  the  colony  ? 

Which  are  the  best  walkers?  Which  are  swiftest  of 
flight? 

Which  are  of  most  importance  to  man? 

Compare  as  to  the  relative  development  of  all  the  parts. 

If  the  paper  wasp  bites  wood,  and  the  honeybee  bites 
nothing  harder  than  wax,  which  should  you  expect  would 
have  the  stronger  mandibles?  Is  it  so  in  fact?  Have 
you  discovered  that  there  is  a  similarly  close  relation 
between  the  structure  of  all  organs  and  the  work  they 
have  to  do? 

THE  BLACK  BLISTER  BEETLE. 

(Epicauta.) 

Haunts.  —  This  beetle  is  very  common  in  autumn,  and 
is  very  easily  collectible.  It  will  answer  well  for  class 
use,  though  a  larger  species,  if  avail- 
able, might  be  more  satisfactory  for 
a  first  examination.  It  is  narrowly 
oblong  in  outline,  uniform  jet  black 
in  color,  and  is  found  on  the  flower 
clusters  of  goldenrod,  thorough- 
wort,  and  ragweed,  and  not  infre- 
quently  on  the  vines  of  potato, 

tomato,  and  clematis.  In  some  local- 
BLACK  BLISTER  BEETLE       .  .          ,  .     ,        ,  ,         ,    , 

x  2.  ities  this  beetle  is  replaced  by  re- 


THE  BLACK  BLISTER  BEETLE.  75 

lated  species,  which  resemble  this  one  closely  in  size  and 
form,  but  which  are  variously  striped.  These  afre  all  blister 
beetles. 

Blistering  Property.  —  In  collecting  and  studying  them, 
they  should  be  handled  with  forceps  and  needles,  and  not 
with  the  fingers ;  for,  when  handled,  there  exudes  from 
the  joints  of  the  abdomen  a  yellowish  fluid  secretion  con- 
taining cantharidin,  and  possessing  the  power  of  blistering 
the  skin  when  coming  in  contact  with  it  in  sufficient 
amount.  This  property  is  retained  even  when  the  insects 
are  dried,  making  them  valuable  to  the  apothecary. 

Collecting.  —  A  bottle  is  all  the  apparatus  needed  for 
collecting  this  insect,  —  an  empty  bottle  for  live  speci- 
mens, or  a  cyanide  bottle  for  dead  ones.  They  may  be 
pushed  from  the  flowers  or  leaves  directly  into  the  bottle 
with  its  stopper. 

Study  the  Live  Insect.  —  Observe  the  nature  and  extent 
of  its  injury  to  the  plants  on  which  it  feeds.  Has  it  any 
competitors  for  the  food  these  plants  supply  ? 

Observe  the  action  of  its  wings.  Pick  up  with  forceps 
a  live  specimen  by  an  antenna,  and  observe  how  it  opens 
and  uses  its  wings.  Put  it  down  again,  and  observe  how 
it  folds  them  up. 

Study  specimens  from  the  cyanide  bottle. 

External  Features.  I.  The  Head.  —  Observe  that  the 
head  is  narrowed  behind,  to  form  a  sort  of  neck  at  its 
junction  with  the  prothorax. 

Observe  the  size  and  position  of  eyes  and  ocelli. 

Examine  an  antenna,  and  study  its  structure  and 
action.  Draw. 

Find  in  the  mouth  parts  labrum,  well-developed  man- 
dibles, maxilla3  with  prominent  palpi,  and  labium  with 


T6  INSECTS. 

shorter  palpi.     Separate   and  draw.     For  what  kind  of 
feeding  is  this  mouth  adapted  ? 

II.  The  Thorax.  —  Note  the  relative  development  of  the 
thoracic  segments.     Which  is  largest  ?     Observe  the  con- 
tour of  the  surface  of  the  thorax  at  the  junction  of  the 
legs  and  of  the  wings  with  the  body.     The  cavities  into 
which  the  coxae  are  fitted  are   called  the  coxal  cavities. 
The  coxal  cavities  of  the  fore  legs  are  open  behind;  i.e., 
not  surrounded  posteriorly  by  the  thoracic  wall. 

III.  The  Legs.  —  Examine  the  legs.     Flex  and  extend 
them,  and  observe  the  action  of  the  joints.     Find  in  each, 
leg  coxa,  trochanter,  femur,  tibia,  and  tarsus.     How  many 
segments  in  the  fore  and  middle  tarsi  ?     How  many  in 
the  hind   tarsi  ?     Which    segment   of   the   hind   tarsi   is 
largest  ?      Observe  that  the  two  claws  of  each  tarsus  are 
cleft  to  their  bases,  and  appear  as  four  claws. 

IV.  The  Wings.  —  Lift   the    chitinous    sheaths    (wing 
covers  or  elytra)  which  meet  by  smooth  edges  along  the 
median  dorsal  line,  completely  covering  the  posterior  part 
of  the  body. 

Extend  them  at  right  angles  to  the  body,  and  examine 
the  wings.  Observe  how  they  lie  folded.  With  forceps 
seize  a  wing  by  its  costal  margin,  and  draw  it  forward. 
Observe  how  it  opens  automatically  when  drawn  forward. 
Compare  this  method  of  folding  with  that  already  studied 
in  the  grasshopper. 

V.  The    Abdomen.  —  Study    the    abdomen.      Compare 
upper  and  lower  surfaces.     Count  the  segments.     Com- 
pare this  abdomen  in  form  and  structure  with  that  of  the 
Hymenoptera  studied.     Why  has  the  beetle  less  need  for 
flexibility  in  this  part  than  the  bee  ? 

Development.  —  From  July  to  October  inclusive,  the 
eggs  of  the  black  blister  beetle  are  laid  in  masses  of  more 
than  a  hundred  in  shallow  excavations  in  the  soil.  The 


OTHEK   BEETLES.  77 

warm,  sunny  locations  frequented  by  locusts  are  usually 
chosen.  The  eggs  are  usually  covered  lightly  with  earth, 
and  are  left  to  hatch. 

The  metamorphosis  of  blister  beetles  is  very  peculiar 
and  exceptional.  An  active  larva  (triungulin),  with  good 
legs  for  getting  about,  is  hatched  from  the  egg.  It  runs 
about,  searching  the  ground  over  for  a  buried  cluster  of 
locust  or  grasshopper  eggs.  At  this  stage  it  possesses 
great  powers  of  endurance,  being  able  to  live  a  fortnight 
without  food.  If  successful  in  finding  an  egg  cluster,  it 
settles  down,  and  begins  to  eat  the  eggs.  After  two  molts, 
it  becomes  a  heavy,  footless  larva.  After  several  additional 
molts,  and  after  attaining  its  growth,  it  quits  the  remains 
of  the  egg  cluster,  goes  deeper  into  the  soil,  and  trans- 
forms into  a  pupa.  Later  it  emerges  as  the  imago  already 
studied.  For  a  full  account  of  the  transformations  of  this 
and  of  other  blister  beetles,  read  the  articles  by  Dr.  C.  V. 
Riley,  in  Vol.  XII.  of  the  "American  Naturalist." 

If  eggs  of  the  blister  beetle,  and  also  the  locust  eggs 
on  which  it  feeds,  can  be  found  and  suitably  placed,  all 
the  transformations  may  be  seen  taking  place  in  the 
course  of  a  few  weeks. 

This  insect  is  a  representative  of  the  group  Coleoptera 
(or  sheath- winged  insects).  NO.  i. 

Other  Beetles.  —  Perhaps  no  other  beetle 
is  so  easily  obtainable  in  autumn,  in  supply 
sufficient  for  class  use,  as  the  black  blister 
beetle ;  yet,  lest  it  should  not  be  found 
when  wanted,  cuts  of  four  other  common 
beetles,  which  will  answer  equally  well  SOLDIER  BEETLE 

.  ,  .    .        ,  (Chauliognathus). 

for  study  here,  are  subjoined  :  — 

No.  1  is  a  soldier  beetle,  closely  resembling  the  black 
blister  beetle  in  structure,  and  frequenting  the  same 
haunts.  It  is  yellowish  brown  in  color  above,  with  a 


78 


INSECTS. 


No. 


large   black   spot  on    each  elytron,   and  another  on   the 
pronotuin.     It  is  found  on  the  flower  clusters  of   many 

Composite,  and  may  confidently 
be  looked  for  on  thoroughwort * 
blossoms. 

No.  2  is  an  elegant  black 
beetle,  beautifully  banded  with 
yellow.  It  is  often  found  in 
the  clusters  of  goldenrod,  or  on 
the  leaves  of  locust  trees,  in 
which  it  deposits  its  eggs. 

No.   3  is  a  brick-red  beetle, 
with  round,  black  spots.     It  is 
found  singly,  or  a  very  few  to- 
gether,  on   the    leaves    of   the 
LOCUST  BORER  BEETLE  (slightly  larger  species  of  milkweeds.2 

enlarged).  ,T  .  ..        ,  ,      , 

No.    4    is    a    smooth,    black 

beetle,  with  polished  head  and  prothorax,   and  striated 
elytra.     It  is  often  seen  running  about   brick  walks  in 

No.  4. 


No.  3. 


RED  MILKWEED  BEETLE, 
Tetraopes  (natural  size). 


HARPALUS  BEETLE 
(slightly  enlarged) . 


damp  weather,  and  is  nearly  always  to  be  found  by  over- 
turning boards,  logs,  stones,  etc. 

Situations  for   Collecting.  —  Beetles   are   found   every- 
where, and   are   easily   recognized   by   their   elytra   and 

1  Eupatorium.  2Asclepias. 


OTHER   BEETLES.  79 

biting  mouth  parts.  A  number  of  the  common  forms 
should  be  studied  and  compared,  in  order  to  get  a  good 
general  idea  of  the  group.  A  number  of  species,  both 
large  and  small,  are  attracted  by  a  light  at  night.  If  a 
strong  light  be  placed  in  a  window,  they  may  be  expected 
on  the  screen  outside,  together  with  swarms  of  moths 
and  other  insects.  Beetles  are  very  commonly  found 
under  the  bark  of  logs  and  stumps  and  in  decaying 
wood.  They  may  be  found  along  a  railroad  track,  under 
discarded  "cross-ties"  or  "sleepers."  Some  gayly  colored 
little  beetles  are  found  on  flowers;  others  are  common 
in  shallow  ponds,  where  they  may  easily  be  taken  with 
a  net.  These  are  among  the  most  interesting  and  attrac- 
tive of  aquarium  specimens.  "Whirligig  beetles"  may 
usually  be  found  on  the  surface  of  still  water,  gyrating  in 
large  companies. 

Study  a  number  of  the  most  diverse  forms  obtainable, 
following  the  outline  given  for  the  black  blister  beetle. 
Then  make  a  comparative  study  of  the  structure  of  all 
the  beetles  collected. 

Other  common  larval  forms  may  be  found,  as  "  grubs  " 
and  "  wire  worms  "  in  the  soil,  and  as  "  borers  "  in  wood. 
Some  larvae  may  easily  be  dug  with  a  strong  knife  from  a 
well-rotted  log  or  stump. 

Pupae  will  often  be  found  in  similar  situations. 

Test  of  Strength.  —  Select  one  of  the  stoutest-looking 
live  beetles  to  be  found,  and  make  this  simple  test  of 
its  strength :  Mold  a  saddle  of  stiff  putty  that  will  just 
fit  over  its  back  without  interfering  with  the  action  of 
its  legs.  Hollow  this  out  above,  and  pour  shot  into  it. 
Make  the  load  all  that  the  beetle  can  walk  away  with. 
Then,  with  delicate  scales,  weigh  the  load,  and  also  the 
beetle.  If  a  man  weighing  one  hundred  and  fifty  pounds 
were  as  strong  in  proportion,  how  much  could  he  carry  ? 


80  INSECTS. 

THE  BLUEBOTTLE  FLY. 

(Lucilia  ccesar.) 

Characteristics.  —  This  is  the  loudly  buzzing  fly  that 
gets  into  our  pantries  and  cellars.  Its  body,  especially 
its  abdomen,  is  of  a  brilliant  bluish-green  color.  It  is 
larger  than  the  common  house  fly,  and  therefore  better 
for  a  first  examination. 

If  a  bit  of  fresh  meat  be  exposed  out  of  doors  in  warm 
weather,  in  a  very  few  minutes  a  number  of  these  flies 
will  be  attracted  to  it.  They  may  be  taken  with  a  net. 

Study  of  a  Live  Specimen. — Note  the  sound  of  their 
buzzing  in  ordinary  flight.     Then  catch  one,  and,  being 
careful  not  to  disable  it  in  any  way, 
hold  it  by  the  feet,  leaving  its  wings 
free.     Note  that  the  buzzing  is  in  a 
higher  key.     Then  hold  both  wings 
and  legs  so  that  neither  can  move, 
and  note  that  the  sound  still  con- 
tinues, and  that  the  pitch  is  again 
BLUEBOTTLE  FLY         raised.     This  last  sound  is  probably 
produced  by  vibrations  set  up  in  the 
spiracles  by  manipulation  of  the  currents  of  air. 

Study  its  feeding  habits.  It  is  not  shy :  it  will  eat 
freely  from  a  bit  of  meat  held  with  the  fingers.  Watch 
it  with  a  lens.  Study  the  appearance  and  action  of  its 
proboscis.  Observe  that  it  is  somewhat  two-jointed;  that 
the  first  joint  is  somewhat  retractile  into  a  cavity  in  the 
base  of  the  head;  that  the  second  joint  folds  up  on  the 
first  with  a  hingelike  action  when  not  in  use;  and  that 
the  second  joint  ends  in  blunt  expansion,  which  consists 
of  two  flaps,  that  are  separated  in  feeding,  and  applied  to 
the  surface  of  the  food. 


THE   BLUEBOTTLE   FLY.  81 

The  action  of  these  flaps  may  be  studied  under  the 
microscope.  For  this  purpose  the  common  house  fly  is 
better,  being  smaller.  Proceed  as  follows  :  Wet  one  side 
of  a  large  crystal  of  granulated  sugar,  place  it  on  a  slide, 
and  let  it  dry  fast.  Place  the  slide  on  the  stand  of  the 
microscope,  blocking  up  one  edge  at  a  decided  angle. 
Focus  on  the  crystal  of  sugar  with  the  lowest  power  of 
your  instrument.  Take  your  apparatus  thus  prepared 
into  a  room,  or  other  place  where  there  are  many  hungry 
flies,  and  wait  for  one  to  alight  on  the  slide,  and  apply  the 
opened  leaves  or  flaps  of  the  end  of  its  proboscis  to  the 
sugar.  Focus  carefully,  and  record  your  observations  on 
the  action  of  this  part. 

Examine  a  bluebottle  fly  that  has  been  freshly  killed 
in  a  cyanide  bottle. 

External  Anatomy.  —  Observe  the  general  contour  of 
the  body,  the  shortness  of  the  abdomen,  and  the  speciali- 
zation of  the  thoracic  region. 

Note  the  shape  of  the  head,  the  freedom  of  its  movements, 
the  position  and  size  of  the  eyes  and  ocelli. 

Find  the  short  antennae.  Remove  one,  being  careful 
to  get  it  off  entire,  and  examine  it  with  the  microscope. 
Find  in  it  six  segments,  as  follows:  — 

1.  A  small  subquadrate  first  or  basal  segment,  bear- 
ing on  one  side,  near  its  base,  four  conspicuous  bristles. 

2.  A    roundish   second    segment,    bearing    one    stout, 
straight  bristle,  and  a  number  of  smaller  ones. 

3.  A  large,  oblong  segment,  much  the  largest  in  the 
antenna,  its  surface  sprinkled  with  minute  pits  and  hairs. 
This  segment  at  first  appears  to  be  terminal,  but  it  is  in 
fact  much  produced  laterally. 

4.  Two  minute  segments,  attached  near  the  base  of  the 
third  segment,  and  forming  a  sort  of  pedicel  for  the  ter- 
minal segment. 

NEED.  ZOOL.  — 6 


82  INSECTS. 

5.  The  terminal  segment,  which  is  expanded  into  a  long, 
feathery  tip.  Draw. 

Mouth  Parts.  —  The  study  of  the  mouth  parts  is  not  so 
easy.  The  parts,  being  soft,  are  difficult  of  separation. 
That  they  are  all  combined  into  a  sort  of  proboscis  has 
been  seen  already.  The  sheath  of  this  proboscis  consists 
of  labium  and  labial  palpi,  grown  together,  and  split  down 
the  median  line  of  the  second  joint  of  the  proboscis  in 
front.  At  its  tip  are  the  two  flaps  already  noticed.  The 
structure  of  this  tip  may  be  studied  as  follows:  Kill  a  fly 
in  the  cyanide  bottle,  and  at  once  cut  off  its  head.  Place 
the  head  flat  on  a  slide,  face  upward,  and  apply  pressure 
to  the  center  of  the  head  with  the  point  of  a  pencil.  This 
will  cause  the  proboscis  to  expand  fully.  When  so  ex- 
panded, apply  a  drop  of  turpentine  and  a  cover  glass  to  its 
tip,  and  fasten  the  cover  glass  down  with  a  clip  before 
removing  pressure.  The  inner  surfaces  of  the  two  flaps 
will  be  fully  exposed,  and  may  be  studied  at  leisure. 
Observe  the  nearly  parallel  ridges  on  these  surfaces. 
Observe  that  they  run  transversely.  Consider,  then,  that 
the  proboscis  is  moved  backward  and  forward  in  feeding, 
and  you  will  see  that  the  structure  of  these  parts  explains 
their  action,  and  that  the  rasping,  back-and-forward  motion 
utilizes  the  rasping  surfaces  formed  by  these  transverse 
ridges.  Draw. 

Within  the  sheath  of  the  proboscis  there  are  two  small, 
elongated  organs,  one  above  the  other,  channeled  along 
their  inner  faces,  making  a  tubular  passage,  through  which 
food  is  sucked  into  the  pharvnx.  Mandibles  are  wanting. 
Maxillae  are  represented  by  rudimentary,  one-jointed  palpi, 
which  arise  from  near  the  middle  of  the  basal  joint  of  the 
proboscis. 

Thorax,  Abdomen,  and  Appendages. — Observe  the  shape 
of  the  thorax,  and  the  extreme  specialization  of  its  middle 


THE   BLUEBOTTLE   FLY.  83 

segment.  Remembering  that  the  top  of  the  thorax  con- 
tains the  wing  muscles,  can  you  see  any  reason  for  the 
specialization  of  the  mesothorax,  and  for  the  suppression 
of  the  other  segments  ? 

Observe  the  shape,  size,  position,  and  texture  of  the 
single  pair  of  developed  wings.  Observe  that  these  are 
produced  backwards  at  their  bases  in  two  short  mem- 
branes (the  alulets).  Draw. 

On  the  sides,  half  concealed  by  the  alulets,  find  a 
pair  of  knobbed,  threadlike  appendages  (the  halteres,  or 
balancers).  Observe  that  these  spring  from  the  narrow 
inetathorax.  They  represent  the  second  pair  of  wings. 
Remove,  examine  with  low  power,  and  draw. 

Observe  the  size  and  position  of  the  legs.  For  what 
kind  of  locomotion  are  they  adapted  ?  Examine  one  with 
a  lens,  to  find  the  usual  parts.  How  many  segments  in 
the  tarsus  ?  Observe  the  two  claws  at  the  end  of  the  ter- 
minal segment,  and  the  pulvilli  (or  sucking  disks)  beneath 
it.  It  is  by  means  of  these  pulvilli  that  a  fly  walks  up  a 
windowpane  or  across  the  ceiling.  Count  the  segments 
of  the  abdomen  externally  visible.  Three  terminal  seg- 
ments are  withdrawn  within  the  end  of  the  abdomen,  and 
concealed  like  the  small  joints  of  a  spyglass  within  the 
large  one.  Search  the  sides  of  both  thorax  and  abdomen 
for  spiracles. 

Development.  —  The  development  of  this  insect  can  be 
watched  with  less  time  and  trouble  than  that  of  almost 
any  other;  and,  although  its  early  environment  is  far  from 
being  attractive,  it  teaches  an  important  lesson  in  the 
economy  of  nature.  We  cannot  know  the  important  place 
this  fly  fills  without  knowing  something  of  its  larval  life. 
This  is  true  of  all  insects. 

The  eggs  of  the  bluebottle  fly  are  laid  on  flesh, — 
ordinarily  on  the  carcasses  of  animals  that  have  fallen 


84  INSECTS. 

in  the  woods  and  fields,  —  and  the  larvae  hatched  from 
them  are  popularly  known  as  maggots.  These  render  great 
service  in  the  speedy  removal  of  offensive  substances. 

The  developmental  changes  may  be  studied  without 
discomfort,  as  follows:  Expose  out  of  doors  a  bit  of  lean 
meat,  so  that  the  eggs  may  be  laid  upon  it.  Fill  a  flower- 
pot or  tin  can  or  small  box  with  sand,  and  on  a  chip 
in  the  center  of  it  place  the  bit  of  meat  with  the  eggs 
on  it.  Invert  a  tumbler  over  it,  and  push  the  rim  of  the 
tumbler  down  into  the  sand.  This  will  prevent  the 
escape  of  offensive  odors,  should  such  arise  ;  and  the  whole 
can  easily  be  arranged  so  that  the  developmental  changes 
may  be  witnessed  through  the  glass.  In  a  few  hours  the 
eggs  will  hatch,  and  in  a  few  days  the  larvae  will  be  fully 
grown.  They  will  probably  crawl  beneath  the  chip  or 
into  the  sand,  to  transform  into  pupae.  Upon  the  disap- 
pearance of  larvae,  the  oval  pupae  may  be  looked  for.  They 
may  transform  speedily,  or  may  continue  as  pupae  through 
the  winter,  according  to  the  temperature  and  the  season. 

The  bluebottle  fly  is  a  representative  of  the  group  Dip- 
tera  (or  two-winged  insects). 

Other  Diptera  in  general  may  be  recognized  by  their 
having  but  one  pair  of  developed  wings.  They  are  always 
and  everywhere  abundant  except  in  winter.  Many  beau- 
tiful and  interesting  species  will  be  found  about  the 
flowers  of  autumn.  The  following  illustrative  form  is 
recommended  for  further  study  here. 

THE  BEE   KILLER. 

(Asilus.) 

Characteristics.  —  This  is  the  dust-brown  insect  that 
flits  by  our  path  in  summer  and  autumn  with  such  sud- 
den and  high-pitched  sound  of  wings.  This  sound 


THE   BEE   KILLER.  85 

alone,  once  heard,  is  sufficient  for  recognition  of  the 
insect.  It  is  one  of  the  largest  and  fiercest  of  our  Dip- 
tera.  It  is  an  inch  or  more 
in  length.  It  feeds  princi- 
pally on  honeybees,  pouncing 
upon  them  with  great  swift- 
ness while  on  the  wing.  It 
frequents  dry  pastures  where 
bees  are  feeding.  It  is  often- 
est  seen  when  startled  from 
its  resting  place  upon  a  stick 
or  stone  beside  our  path.  It 

..  ..  BEE  KILLER,  Asilus  (natural  size). 

may  be  captured  by  dexterous 

use  of  the  net.  It  should  be  introduced  into  the  cyanide 
bottle  without  handling,  for  its  beak  is  powerful  enough 
to  wound  the  fingers. 

Study  of  Live  Specimens.  —  Having  flushed  a  bee  killer 
from  its  resting  place,  it  may  be  followed  at  a  proper 
distance,  and  something  may  be  seen  of  its  predaceous 
habits.  Take  time,  while  in  the  field  collecting,  to  ob- 
serve :  — 

1.  The  character  of  its  flight  as  to  speed,  directness,  etc. 

2.  The  length  of  time  spent  on  the  wing  at  one  flight. 

3.  The  course  of  its  flight.     After  one  of  its  swift  sal- 
lies, does  it  usually  return  to  the  same  resting  place  from 
which  it  started  out,  or  to  a  new  one  ? 

4.  The  purpose  of  its  flight.     Does  it  seem  to  be  intent 
on  catching  a  bee  at  every  flight,  or  does  it  sometimes 
seem  to  fly  for  sport? 

5.  Its  feeding  habits.     Try  to  see  one  catch  a  bee  and 
carry  it  away  to  be  eaten.     Wait  quietly  by  until  the 
bee  killer  has  finished  its  repast ;    then  go  and  look  for 
the  remains  of  the  bee.     What  part  is  left?     Search  the 
spots  from  which  other  bee  killers  are  flushed,  for  the  re- 


86  INSECTS. 

mains  of  other  bees.    In  this  way  3-011  will  get  an  idea  of  the 
extent  of  its  depredations  on  the  population  of  the  hive. 

Capture  a  few  good  specimens  to  be  used  in  studying 
the  external  peculiarities.  Note  specially  the  length  of 
the  abdomen,  the  strength  of  the  beak,  the  size  and  rough- 
ness of  the  legs,  and  the  position,  size,  and  strength  of  the 
wings.  Make  drawings  of  antennee,  mouth  parts,  legs, 
wings,  halteres,  etc.,  and  compare  with  those  of  the  blue- 
bottle fly. 

THE  CABBAGE  BUTTERFLY. 

(Pieris  rapce.) 

This  is  the  small  white  butterfly  with  black  wing  tips, 
too  abundant  about  our  gardens.  Something  of  its  habits 

will  have  been  seen  already, 
for  it  is  commonly  found 
feeding  with  the  sulphur 
butterfly.  Collect  now  a 
number  of  specimens  to  be 
used  in  studying  it. 

External      Anatomy.  — 

FEMALE  CABBAGE  BUTTERFLY,  Pieris     Follow  the   plan   of  study 
rapK  (from  Riley).  .  .    r  / 

laid  down  in  the  "  Prelimi- 
nary Lesson"  for  the  sulphur  butterfly.  When  studying 
the  mouth  parts,  note  that  the  coiled  organ,  which  has 
been  called  the  tongue,  consists  of  two  elongated  organs, 
grooved  on  their  inner  edges,  and  placed  side  by  side,  so 
that  the  grooves  meet,  and  form  a  tubular  food  passage 
between  them,  and  that  these  two  organs  are,  in  fact, 
the  much  modified  lacinia  of  maxillae. 

A  few  convenient  descriptive  terms  applying  to  the 
wings  need  to  be  learned  here.  The  wings,  being  some- 
what triangular  in  outline,  present  three  margins  and 
three  angles.  The  anterior  margin  is  called  the  costal 


THE   CABBAGE   BUTTERFLY.  87 

margin,  or  more  commonly  the  costa;  the  margin  farthest 
from  the  body  is  called  the  outer  margin;  the  other  mar- 
gin is  called,  on  the  fore  wings  the  hind  margin,  on  the 
hind  wings  the  internal  margin.  The  angle  by  which  the 
wing  joins  the  body  is  called  the  base;  the  angle  between 
the  costal  and  outer  margins  is  called  the  apex;  the 
other  angle  is  called  the  posterior  angle  on  the  fore  wings, 
the  anal  angle  on  the  hind  wings.  The  branches  of  the 
subcostal  vein  are  called  the  subcostal  veinules,  and  like- 
wise those  of  the  median  vein  are  called  median  veinules; 
and  both  are  numbered  first,  second,  third,  etc.,  from  the 
front.  On  the  basal  half  of  each  wing,  between  the  sub- 
costal and  median  veins,  is  an  obovate  inclosure,  called 
the  discal  cell,  or  more  often  simply  the  cell.  The  space 
outside  this,  occupied  by  the  terminal  veinules,  is  called 
the  discal  space,  or  often  simply  the  disk.  Extending 
across  the  ftisk  from  the  cell  to  the  outer  margin  of  the 
wing  is  a  short,  straight  vein  situated  about  halfway  be- 
tween the  subcostal  and  median  veins,  but  appearing  not  to 
be  a  branch  of  either,  and  hence  called  the  independent  vein.1 

1  The  names  of  veins  here  given  are  those  found  in  nearly  all  our 
descriptive  works  on  butterflies  and  moths.  There  has  been  little  uni- 
formity hitherto  in  the  names  used  by  writers  in  the  different  groups, 
each  of  the  principal  groups  having  developed  a  nomenclature  of  its  own. 
Professor  Comstock  has  proposed  for  the  veins  of  the  wings  of  all  insects 
a  uniform  nomenclature  which  seems  likely  to  be  adopted.  Applying 
this  system  to  butterflies  and  moths  (Lepidoptera) ,  the  principal  veins  are 
as  follows :  — 

Costa.  —  On  the  costal  edge  of  the  wing. 

Subcosta.  —  Improperly  called  the  costa  by  writers  on  the  Lepidoptera. 

Radius.' —  Improperly  called  the  subcosta  by  writers  on  the  Lepidoptera. 

Media.  —  The  base  of  this  vein  is  wanting,  and  its  branches  are  joined 
to  adjacent  veins.  It  is  three-branched.  Its  middle  branch  is  the  so-called 
independent  vein. 

Citbitus.  — This  vein  is  two-branched,  but  appears  to  be  three-branched 
in  most  butterflies,  as  the  third  branch  of  media  is  joined  to  it. 

Anal  Veins.  —  There  may  be  one,  two,  or  three  of  these.  In  most 
butterflies  there  is  one  anal  vein  in  the  fore  wing,  and  there  are  two  in 
the  hind  wings. 

Costa,  subcosta,  and  the  anal  veins  are  simple  in  all  Lepidoptera. 


88 


INSECTS. 


Make  an  enlarged  drawing  of  both  wings  of  one  side, 
naming  all  these  parts  on  the  drawing. 

Development.  —  In  almost  any  cabbage  patch  during 
summer  and  autumn  this  insect  may  be  found  in  all 
stages  of  development.  Collect  and  observe  :  — 

1.  Eggs.  These  will  be  found  attached  singly,  usually 
to  the  lower  surfaces  of  cabbage  leaves.  They  are  quite 
minute,  and  are  pale  yellowish  in  color. 
They  should  be  taken  with  the  leaves 
to  which  they  are  attached,  and  not 
removed  from  the  leaves  until  they 
are  to  be  studied. 

2.  Larvce.  These  are  found  most 
abundantly  on  the  fresh  but  slightly 
expanded  leaves  and  on  both  surfaces. 
Some  will  be  found  feeding,  others 
resting.  All  sizes  will  be  found  com- 
mingled. 

Lift  one  that  is  resting,  from  the 
leaf,  to  observe  the  layer  of  silk  in 
which  its  feet  are  entangled.  This  silk  is  spun  from  a 
spinneret  (modified  labrum)  below  the  mouth.  A  small 
larva  may  sometimes  be  seen  actively,  and  even  somewhat 
violently,  swinging  its  head  from  side  to  side  as  it  lays 
down  this  layer  of  silk,  thread  by  thread. 

Watch  a  large  larva  that  is  feeding,  to  see  how  methodi- 
cal is  its  habit. 

How  does  a  larva  walk?  Can  it  walk  more  easily  on 
the  side,  or  on  the  margin,  of  a  leaf  ? 

Observe  the  nature  and  extent  of  the  injury  done  to 
the  cabbages  by  these  larvae. 

Observe  later  their  hours  of  feeding. 
Observe  whether  they  are  found  in  the  same  positions 
on  sunshiny  as  on  cloudy  days. 


LARVA  AND  PUPA  OF 
CABBAGB  BUTTER- 
FLY (from  Riley). 


THE   CABBAGE   BUTTERFLY.  89 

Observe  the  effect  on  them  of  wet  weather  and  of  dry ; 
of  hot  weather  and  of  cold. 

Collect  larvae  of  all  sizes,  and  keep  them  supplied  with 
cabbage  leaves  until  wanted  for  further  examination. 

3.  Pupce  or  chrysalides.     These  have  an  angular,  chi- 
tinous  case,  something  less  than  an  inch  long,  and  pale 
and   inconspicuous.     One  will  occasionally  be  found  at- 
tached to  a  cabbage  leaf,  but  more  often  to  the  under  side 
of  a  fence  board,  or  to  a  post  some  few  yards  distant  from 
the  cabbages.     There  is  little  or  no  attempt  at  conceal- 
ment; but,  if  one  be  'not  found  readily,  it  may  easily  be 
obtained  in  a  few  days  by  keeping  in  confinement  a  few 
full-grown  larvae,  and  this  will  afford  opportunity  for  ob- 
serving the  transformation.     For  this  purpose  a  few  of 
the  largest  larvae  (they  should  be  more  than  an  inch  long) 
may  be  placed  in  an  ordinary  jelly  glass,  with  pieces  of 
fresh  cabbage  leaves,  covered  with  the  tin  top  to  prevent 
the  drying-up  of  the  leaves,  and  left  there  until  the  trans- 
formation takes  place. 

When  a  chrysalis  has  been  obtained,  note  its  location 
and  attachments.  At  its  posterior  end  is  a  circlet  of 
hooks,  called  a  cremaster,  fastened  firmly  into  a  button 
of  silk  that  was  spun  by  the  larva.  Around  its  thoracic 
region  is  a  supporting  loop  of  silk  attached  at  both  ends 
to  the  support  above.  How  does  a  thing  so  inert  become 
suspended  in  such  a  peculiar  fashion  ? 

4.  Imagoes.     These  should  be  obtained  from  the  chry- 
salides.    All  that  is' necessary  is  the  keeping  of  the  chry- 
salides in  a  moderately  warm  place,  and  in  a  good  place 
for  observation,  for  a  short  time.      This  will  be  advan- 
tageous on  two  accounts  :  (1)  it  will  afford  an  opportunity 
for  observing  the  final  transformation,  —  the  rupture  of  the 
chrysalis,  the  emergence  of  the  imago,  and  the  expansion 
and  drying  of  its  wings,  —  a  truly  wonderful  transforma- 
tion, that  ought  to  be  seen  by  every  one  ;  and  (2)  it  will 


90  INSECTS. 

afford  an  opportunity  for  seeing  something  of  the  effects 
of  certain  parasites  of  the  cabbage  butterfly,  chief  among 
which  is  a  little  black  ichneumon  fly.  This  fly  lays  its  eggs 
in  punctures  in  the  skin  of  the  larva.  The  eggs  hatch  out 
little  fly  larvae,  which  feed  upon  the  vitals  of  the  butterfly 
larva.  The  latter,  if  not  killed  by  these  parasites  before 
attaining  its  growth,  becomes  a  chrysalis,  inside  which  the 
fly  larvae  continue  their  growth  and  transformations. 
Finally  there  issues  from  the  chrysalis,  not  a  butterfly, 
but  a  swarm  of  little  black  ichneumon  flies.  If  half  a 
dozen  chrysalides  be  kept,  an  infested  one,  or  several,  will 
probably  be  found.  If  a  chrysalis  looks  much  blacker 
than  the  others,  it  is  surely  infested;  and,  if  placed  in  a 
small  vial,  the  ichneumon  flies  may  be  caught  when  they 
issue  forth. 

Immature  Stages.  —  Study  the  three  preparatory  stages. 
I.   The  Egg.  —  Study  the  egg  to  make  out :  — 

1.  Its  attachment  to  the  leaf. 

2.  Its  shape. 

3.  Its  surface  markings. 

II.   The  Larva.  —  Study  the  larva.     Observe :  — 

1.  The  plainly  distinguishable  head. 

2.  The  cylindrical  body,  without  distinguishable  thorax 
and  abdomen.     Count  the  segments. 

3.  Three  pairs  of  true  legs  on  the  first  three  body  seg- 
ments.     These  mark  the  portion  of  the  body  which  is 
later  to  become  the  thorax. 

4.  Five  pairs  of  false  legs,  called  prolegs  (abbreviated 
from  "  prop  legs  "),  borne  on  the  sixth,  seventh,  eighth, 
ninth,  and  last  body  segments.   - 

5.  Spiracles,  a  pair  on  each  of  the  body  segments  ex- 
cept the  second,  third,  and  the  last  two,  opening  at  the 
sides.     The  absence  of  spiracles  on  the  second  and  third 
segments  marks  these  as  the  ones  which  are  to  bear  the 


THE   CABBAGE   BUTTERFLY.  91 

wings.      Powerful   wing    muscles    are   to   be    developed 
within  them. 

Kill  a  large  larva  by  placing  a  drop  of  chloroform  upon 
its  head,  or  by  any  other  convenient  method,  and  with  a 
good  lens  examine  :  — 

1.  Its  head,  as  seen  from 
the    front    and    from    be- 
neath.    Make  out :  — 

(a)   Ocelli    situated    on 

the    front     of    the     lateral      DIAGRAM  OF  LARVA  (x  2):  e,  simple 

prominences  of  the  head.          fes.  ?n,  ^  f™nt  °f*a£  hfd; 

*  I,  ]omted  legs  attached  to  the  three 

How   many,    and   how    ar-  thoracic    segments;     sp,    spiracle 

ranged?  openings;  pr,  prolegs. 

(5)  A  labrum,  a  little  flap  of  membrane  above  the  mouth. 

(c)  A  pair  of  rather  prominent  biting  mandibles  which 
meet  by  serrated  edges. 

(d)  On  either  side  of  these  a  very  rudimentary  stump 
of  an  antenna,  here  found  situated  lower  on  the  head  than 
in  the  perfect  insect. 

(e)  Below  the  mandibles,  a  pair  of  very  rudimentary 
maxillce.     They  are  but   fleshy  prominences   here,  made 
recognizable  by  a  pair  of  minute  appendages  (palpi)  at 
the  tip  of  each. 

(/)  Between  and  below  the  maxillae  is  the  larger  la- 
brum with  its  very  minute  rudiments  of  palpi,  and  a 
median  appendage  of  special  structure  (a  slender  horny 
tube,  which  serves  as  a  spinneret) .  Through  it  is  exuded, 
from  glands  in  the  head,  a  liquid,  which  dries,  immediately 
on  exposure  to  the  air,  into  the  silken  thread  which  the 
larva  spins  over  the  leaves. 

Compare  this  mouth  with  that  of  an  adult. 

2.  The    covering   of    the   skin.      What    kind   of    out- 
growths can  you  find  with  a  lens  ? 

3.  Its  thoracic  legs.     Make  out :  — 
(a)  That  they  are  jointed. 


92  INSECTS. 

(5)  That  they  end  in  a  horny,  hook -like  tip. 
4.  Its  prolegs.     Make  out :  — 

(a)  That  they  are  more  membranous. 

(6)  That  they  end  in  a  circlet  of  minute  hooks  exactly 
adapted  for  catching  into  a  layer  of  silken  threads,  and 
probably  more  serviceable  to  the  caterpillar  than  are  its 
true  legs. 

Compare  this  locomotor  apparatus  with  that  of  an  adult. 
III.    The  Pupa.  —  Study  the  chrysalis.     Observe  :  — 

1.  The  consolidation  of  head  and  thorax. 

2.  The  relative  freedom  of  the  abdomen  and  its  capacity 
for  a  slight  twisting  motion. 

3.  The  shape  and  surface  markings  of  the  chrysalis,  and 
the  structure  of   the  cremaster,  in   which   the   abdomen 
terminates. 

4.  The  chitinous  sheaths  or  cases  of  the  appendages  of 
the  body  overlapping  on  the  ventral  surface.     The  cen- 
tral ridge  is  that  formed  by  the  tongue  case.     Those  next 
on  either  side  of  it  cover  the  first  pair  of  legs.     The  next 
cover  the  second  pair  of  legs.     The  next  are  the  antennae 
cases.     The  next  and  largest  are  the  wing  cases.     The 
third  pair  of  legs  is  concealed  beneath  the  wing  cases. 
When  the  chrysalis  is  first  formed,  these  parts  are  soft  and 
easily  separable,  but  they  become  very  solidly  coherent 
in  an  old  chrysalis. 

5.  The  spiracles  of  the  abdomen  in  their  normal  posi- 
tion.    The  one  on  the  first  thoracic  segment  has  been 
crowded  backward  until  it  appears  between  the  first  and 
second  segments. 

From  a  comparison  of  larva  and  imago,  it  becomes  evi- 
dent that  the  quiescent  pupal  period  is  the  period  of 
greatest  developmental  changes.  It  should  be  noted,  how- 
ever, that  these  changes  have  been  begun  in  the  larva; 
that  the  insect  begins  its  pupal  period  in  possession  of 
the  rudiments  of  its  perfect  organs. 


THE   LIFE  PROCESS  IN   INSECTS.  93 

It  should  be  noted  also,  in  comparison  of  larva  and  imago, 
that  there  is  an  entire  change  of  life  habits  and  of  instincts. 
That  there  is  no  traceable  connection  between  the  instincts 
of  the  larva  and  those  of  the  adult,  is  an  interesting  fact. 


PUPA  (x  3) :  h,  head;  e,  eye  case;  th,  thorax;  ant,  antenna  case;  tc,  tongue 
case;  Ic,  cases  of  front  and  middle  legs;  we,  wing  cases;  sp,  spiracles; 
a,  abdomen ;  cr,  cremaster. 

Butterflies  and  moths  constitute  the  group  Lepidoptera 
(or  scaly-winged  insects).  Capture  a  few  of  the  moths 
that  are  attracted  to  a  light  at  night,  and  examine  them, 
to  discover  wherein  moths  differ  from  butterflies. 

THE   LIFE   PROCESS   IN   INSECTS. 

I.  Nutrition.  —  The  food  of  insects  is  so  various,  that 
diverse  organs  are  necessary  for  seizing  and  preparing  it 
for  digestion.  The  mouth  parts  normally  present  are 
(1)  a  labrum;  (2)  a  pair  of  mandibles;  (3)  a  pair  of  max- 
illae, each  with  three  free  appendages,  —  lacinia,  galea, 
and  palpus  ;  and  (4)  a  labium,  with  its  jointed  palpi. 
Any  of  these  parts  may  be  specialized,  modified,  or  sup- 
pressed, according  to  the  needs  of  the  animal. 


94  INSECTS. 

The  seizure  of  food  is  effected  by  some  or  all  of  these 
parts,  assisted  in  a  few  cases  by  armed  fore  legs.  Masti- 
cation, when  necessary,  is  effected  by  the  mandibles  and 
lacinise  of  the  maxillae 

Two  types  of  insect  mouths  may  be  noted,  adapted 
respectively  (1)  for  sucking  and  (2)  for  biting.  Sucto- 
rial mouths  are  widely  different  in  structure,  some  being 
armed  for  making  punctures,  others  wholly  unarmed.  In 
some  insects  with  suctorial  mouths,  the  pharynx  (some- 
times other  parts  of  the  alimentary  canal)  is  provided 
with  muscles,  and  capable  of  distention,  and,  thus  modified, 
it  becomes  a  pumping  organ. 

Digestion  is  effected  jby  the  crop  (when  present),  gizzard, 
and  stomach,  aided  by  secretions  from  the  salivary  glands 
and  gastric  caeca. 

Circulation  is  effected  at  first  by  the  passage  of  the 
digested  food  through  the  walls  of  the  alimentary  canal, 
out  into  the  blood.  The  blood  bathes  all  the  internal 
organs,  taking  to  each  the  material  needed  for  cell  con- 
struction. It  courses  posteriorly  through  the  body  cavity, 
enters  the  dorsal  vessel  by  lateral  valves,  is  propelled 
forward,  and  passes  out  toward  the  head  through  the 
single  rudimentary  artery. 

Respiration  is  effected  either  by  spiracles  or  by  tracheal 
gills.  The  former  are  adapted  for  aerial,  the  latter  for 
aquatic,  respiration.  Spiracles  are  situated  on  the  sides 
of  the  body,  and  open  into  tracheae,  which  unite  into 
longitudinal  lateral  trunks,  and  send  their  numerous 
branches  to  every  vascular  part  of  the  body.  Some 
aquatic  insects  have  aerial  respiration  ;  i.e.,  they  obtain 
their  air  supply  from  above  the  surface  of  the  water. 
In  these  the  spiracles  usually  open  beneath  the  wings, 
where  air  is  stored  that  has  been  obtained  at  the  surface 
and  carried  down  below. 

Tracheal  gills  are  adapted  for  breathing  the  air  that 


THE   LIFE   PROCESS   IN  INSECTS.  95 

is  mixed  with  the  water,  or  held  in  solution.  These  are 
delicate  expansions  of  the  body  wall,  and  contain  trachese, 
which  divide  and  subdivide  until  the  smallest  branches 
are  separated  from  the  water  only  by  exceedingly  thin 
membrane.  Through  this  the  air  in  the  tracheae  effects 
exchange  of  gases  with  the  air  in  the  water  outside,  and 
is  thus  purified  and  fitted  for  respiration.  Tracheal  gills 
are  usually  situated  on  the  abdomen,  and  must,  of  course, 
project  into  the  water. 

By  either  of  these  means,  oxygen  from  the  air  is  sup- 
plied to  all  parts  of  the  body;  and  that  is  the  essential 
thing  in  respiration. 

Assimilation  of  food  is  the  business  of  each  individual 
cell.  As  no  division  of  labor  in  society  can  relieve  any 
person  of  the  necessity  of  eating,  sleeping,  and  taking 
exercise,  so  no  physiological  division  of  labor  can  exempt 
any  living  cell  in  the  body  from  the  necessity  of  taking 
from  the  blood  supplied  the  material  necessary  for  its 
own  growth.  Each  individual  cell  of  the  insect  must, 
like  the  one  cell  of  the  amoeba,  absorb  and  assimilate  food 
and  excrete  worn-out  material  for  itself. 

It  is  oxygen  that  puts  the  body  material  in  shape  for 
excretion.  The  food  of  animals,  being  organic,  is  made 
up  of  complex  chemical  compounds,  of  which  carbon  and 
hydrogen  are  abundant  elements.  Oxygen,  in  combining 
with  these  elements,  forms  simple  compounds,  and  breaks 
up  the  complex  ones,  liberating  their  potential  energy  in 
the  form  of  various  physical  and  vital  forces,  —  heat, 
electricity,  nerve  force,  etc. 

The  commonest  products  of  oxidation  are  carbonic- 
acid  gas  and  water.  These  have  to  be  removed  from 
the  body. 

Excretion  is  the  name  of  the  process,  and  it  is  effected 
by  various  organs.  Such  gaseous  molecules  as  escape  into 
the  minute  air  tubes  may  be  exhaled  through  the  tracheae. 


96  INSECTS. 

Such  as  get  into  the  blood  may  be  removed  through  the 
secreting  action  of  the  Malpighian  vessels,  or  may  escape 
by  osmosis  directly  through  the  walls  of  the  alimentary 
canal. 

II.  Reproduction. — All  insects  are  dioecious;  i.e.,  the 
sexes  are  distinct.  Paired  generative  organs  are  found  in 
the  abdomen  beneath  the  dorsal  vessel. 

Nearly  all  insects  are  produced  from  eggs.  For  the 
few  remarkable  exceptions,  and  for  the  presentation  of 
the  interesting  questions  connected  therewith,  the  student 
is  referred  to  the  larger  works  on  entomology. 

Of  the  metamorphoses  of  insects  there  are  two  general 
types:  1.  When  incomplete,  there  emerges  from  the  egg 
a  nymph,  which  differs  from  the  adult  principally  in  size, 
and  which,  when  grown,  transforms  directly  into  a  perfect 
insect ;  2.  When  complete,  the  egg  produces  a  larva, 
usually  a  little  wormlike  creature  with  little  external 
likeness  to  its  parents.  This,  when  grown,  transforms 
into  a  pupa,  which,  after  a  quiescent  period,  again  trans- 
forms when  an  imago  issues. 

It  must  be  borne  in  mind  that  a  few  transformations 
will  not  conform  strictly  to  either  of  these  types,  also 
that  there  is  no  difference  in  kind  between  the  two  types. 
Convenience  is  the  best  reason  for  naming  the  growing 
stage  of  the  one  nymph,  and  of  the  other,  larva. 

It  must  be  observed  that  the  growth  of  the  insect  is 
completed  during  the  larval  or  nymph  stage.  Eating  is 
the  sole  business  of  nymph  or  larva.  But  of  adults,  some 
do  not  eat  at  all,  and  those  that  eat  to  keep  alive  do  not 
grow.  To  reproduce  their  kind,  to  fulfill  their  part  in 
Borne  one  of  nature's  little  groups  of  diverse  forms  of  life, 
and  perhaps  to  enjoy  their  brief  existence,  seem  to  be 
their  mission. 

It  will  be  noticed,  that  of  the  inhabitants  of  field,  forest, 


THE   LIFE  PROCESS   IN  INSECTS.  97 

garden,  and  orchard,  popularly  called  worms,  the  great 
majority  are  not  worms  at  all,  but  the  larvse  of  winged 
insects.  The  student  needs  to  be  reminded  here,  that 
little  or  nothing  is  known  of  the  preparatory  stages  of 
many  of  our  native  insects,  and  that  in  consequence 
neither  their  place  in  nature,  nor  their  importance  to  man, 
can  be  rightly  understood  and  appreciated. 

III.  Voluntary  Motion.  —  The  muscular  system  of  in- 
sects consists,  for  the  most  part,  of  isolated  muscular 
fibers,  attached  to  prominences  on  the  inside  of  its  hollow, 
chitiiious  skeleton.  Those  fibers  which  move  the  body 
segments  are  seen,  upon  dissection,  arranged  in  whitish 
bands  along  the  sides  of  the  body  cavity.  The  strong 
wing  muscles  fill  the  top  of  the  thorax.  Some  of  the 
fibers  that  move  the  appendages  of  the  body  are  attached 
to  tendons. 

The  usual  movable  appendages  of  the  insect  body  are 
antennse,  mouth  parts,  legs,  and  wings.  The  adaptations 
of  legs  and  wings  to  the  habits  of  their  possessors  are  not 
less  striking  than  those  of  mouth  parts.  Insects  have 
been  studied  which  have  legs  adapted  by  their  size,  position, 
and  arrangement,  for  standing,  for  walking,  for  running, 
for  jumping,  for  swimming,  and  for  seizing  prey.  The 
most  striking  modifications  of  wings  are  the  very  common 
ones  already  studied, — the  tegmina  of  Orthoptera,  the 
fore  wings  of  many  of  the  Hemiptera,  and  the  halteres  of 
Diptera. 

But  no  account  of  muscles  and  motive  organs  will  con- 
vey any  adequate  notion  of  insect  activity.  This  needs 
to  be  seen  to  be  appreciated ;  and  half  an  hour  spent  in 
the  open  field  on  a  warm  afternoon,  "  amid  hurrying 
wings  and  scurrying  feet,"  in  careful  observation  of  the 
doings  of  these  tiny  creatures,  will  be  of  profit  in  learning 
a  few  of  the  valuable  lessons  that  cannot  be  put  into 

NEED.  ZOOL.  —  7 


98  INSECTS. 

books.  The  athletic  powers  of  a  few  insects,  the  student 
has  had  an  opportunity  to  test  for  himself.  When  size  is 
taken  into  account,  it  is  probable  that  the  champion  ath- 
letes of  the  world  will  be  found  to  be  insects,  at  least  in 
running,  jumping,  and  flying. 

IV.  Sensation.  —  The  nervous  system  consists  of  a 
double  chain  of  ganglia,  extended  lengthwise  on  the 
floor  of  .the  body  cavity,  and  connected  anteriorly  with 
a  large  cerebral  ganglion  in  the  head  by  a  nerve  each 
side  of  the  gullet.  From  the  cephalic  ganglion  or  brain, 
nerves  go  to  the  eyes  and  other  parts  of  the  head,  while 
each  segment  of  the  body  is  supplied  with  nerve  fibers 
from  a  subjacent  ganglion. 

The  five  senses  known  to  us  are  probably  possessed  by 
all  insects.  The  sense  of  touch,  while  common  to  most 
parts  of  the  body,  is  somewhat  specialized  in  antennse, 
palpi,  and  various  tactile  hairs.  Organs  of  sight  have 
reached  a  wonderful  development  in  the  compound  eyes. 
We  have  no  means  of  knowing  what  may  be  the  limits  of 
the  power  of  vision  in  such  organs.  The  sense  of  smell 
(or  some  other  to  us  unknown  sense)  is  undoubtedly 
present,  enabling  insects  to  find  hidden  food.  Certain 
microscopic  structures  in  the  antennse  are  believed  to  be 
organs  of  smell.  No  undoubted  organs  of  hearing  are 
yet  known;  but  it  is  probable  that  insects  can  hear,  for 
many  of  them  possess  elaborate  sound-producing  appara- 
tus. Supposed  organs  of  taste  have  been  found  in  the 
labium  and  lower  side  of  maxillae. 

The  instincts 1  of  insects  are  the  subject  of  many  books. 
They  are  shown  in  manifold  ways,  and  in  no  two  species 
of  insects  in  precisely  the  same  way.  They  are  too 
diverse  to  admit  of  summarizing  here.  But  the  instincts 

1  "An  instinct  is  a  propensity  prior  to  experience,  and  independent  of 
instruction."  —  PA  LEY. 


A   REVIEW   EXERCISE.  99 

perhaps  most  commonly  noted  are  those  which  guide  to 
proper  methods  of  seeking  security  from  enemies,  to  the 
selection  of  proper  places  for  depositing  eggs,  and  to  the 
construction  of  nests  in  which  to  properly  provide  for 
their  young.  The  hunted  moth,  alighting  on  a  leaf  of 
her  own  color,  and  remaining  motionless,  concealed;  the 
aerial  dragon  fly,  immersing  her  eggs  beneath  the  water ; 
the  butterfly,  depositing  her  eggs  upon  the  leaves  of  a 
plant  which  has  furnished  her,  as  an  adult,  no  food ;  the 
wasp,  making  cells  of  mud,  and  stocking  them  with 
paralyzed  spiders ;  and  the  bee,  constructing  her  math- 
ematical cell,  and  feeding  daily  by  hand  her  growing 
young,  —  all  are  but  the  commonest  illustrations  of  a 
faculty  which  culminates  in  the  social  order  of  some  ant 
communities. 

A  REVIEW  EXERCISE. 

1.  Which   of    the    insects    studied   have   mouth   parts 
adapted  for  biting?     For  sucking?     Which  of  the  latter 
have  mouth  parts  armed  for  puncturing,  as  well  as  adapted 
for  sucking  ?     Which  have  the  mouth  parts  adapted  for 
both  biting  and  sucking  ? 

2.  What  mouth  parts  are  specialized  in  seven  of  the 
insects  studied  (one  from  each  group),  and  what  is  the 
advantage  to  the  insect  of  such  specialization?     What  is 
the  food  of  each  ? 

3.  Which  of  the  insects  studied  breathe  by  spiracles? 
Which  of  these  are  aquatic  ?     Which  breathe  by  tracheal 
gills? 

4.  Give  examples  of  insects  having  legs  adapted  (1)  for 
standing,  (2)  for  walking,  (3)  for  running,  (4)  for  leap- 
ing, (5)  for  swimming,  and  (6)  for  seizing  prey. 

5.  Bring  together  the  drawings  that  have  been  made 
of  legs,  of  wings,  of  mouth  parts,  and  of  antennae,  and, 


100  INSECTS. 

placing  like  parts  together,  study  them  comparatively,  to 
note  the  diverse  modifications  of  parts  that  are  homologous. 

6.  Bring  together,  for  comparative  study,  the  drawings 
that  have  been  made  of   entire  insects,  and  note  which 
body  segments  are  specialized  in  each.     Dissection  of  these 
insects  would  have  revealed  a  corresponding  diversity  in 
the  development  of  the  internal  organs  ;  and  the  study  of 
all  shows  one  plan  of  structure,  with  great  variety  in  the 
details  of  its  execution. 

7.  Study  the  drawings  to  ascertain  whether  the  modifi- 
cations of  wings  and  legs,  and  other  organs,  is  always  in 
harmony  with  the  habits  of  the  insect.     Does  the  insect  do 
with  its  locomotive  appendages  just  what  they  seem  fitted 
for  doing  ?     Could  you  not  tell,  by  looking  at  an  unknown 
insect,  whether  it  spends  the  greater  part  of   its   time 
afoot,  or  a-flying? 

'8.  Special  organs  of  touch  (antennae  and  palpi),  and 
special  organs  of  sight  (eyes  and  ocelli),  are  evident  in  the 
insects  studied.  In  the  adult  dragon  fly,  the  eyes  are 
specialized,  and  the  touch  organs  reduced.  Which  of 
these  two  senses  is  probably  more  serviceable  to  the 
dragon  fly,  and  why?  Why  are  the  eyes  reduced,  and 
the  tactile  organs  specialized,  in  some  beetles  ? 

9.  Take  some  unfamiliar  insect  collected  and  killed  by 
another  person,  and  after  studying  carefully  the  devel- 
opment of  its  parts,  and  their  probable  uses,  write  out 
some  inferences — not  guesses,  but  inferences  from  facts 
of  structure  observed  —  as  to  the  habits  of   the   insect, 
particularly  as  to  its  habits  of   feeding  and  of   locomo- 
tion.    Then  compare  your  inferences  with  the  facts  as 
you  can  learn  them  from  later  observations,  on  the  insect 
alive,  or  from  reading. 

10.  Compare  the  wings  of  a  grasshopper,  bug,  and  bee- 
tle.    Observe  that  in  the  first  two  the  fore  wings  are  pro- 
tective coverings,  as  well  as  organs  of  flight.     And  do  not 


A  LESSON  IN  CLASSIFICATION.  101 

fail  to  note,  that,  just  in  proportion  as  they  become  service- 
able for  protection,  they  become  useless  for  flight.  This 
is  a  good  illustration  of  the  universal  law,  that  precise 
adaptation  to  one  thing  brings  limitations  in  other  things. 
Observe,  also,  that  with  the  decrease  in  usefulness  of 
the  fore  wings,  there  is  an  increase  in  size  of  the  hind 
wings,  —  that  the  hind  wings  become  disproportionately 
large,  and  have  to  be  folded  when  at  rest.  Compare  their 
several  methods  of  folding. 

11.  Which  of  the  insects  studied  have  complete,  which 
incomplete,  metamorphoses  ? 

12.  Which  are  injurious  to  vegetation,  and  during  what 
stage  of  metamorphosis  are  they  most  injurious  ?     Which 
are  directly  beneficial  to  man? 

13.  Which  eat  different  food  in  different  stages  of  life  ? 

14.  Which  are  most  musical  (or  noisy,  if  you  please), 
and  by  what  means  do  such  produce  their  sounds  ? 

15.  Mention   examples   of   the   dependence   of  insects 
upon    mimicry  for   protection.      Which    of    the    insects 
studied  show  the  highest  instincts  in  the  care  of  their 
young?     In  the  construction  of  their  nests? 

A  LESSON  IN  CLASSIFICATION.1 

Have  a  good  supply  of  butterfly  specimens  on  hand, 
before  beginning  the  following  work;  the  more  different 
kinds,  the  better. 

1  This  lesson  outlines  a  simple  and  natural  introductory  method  which 
has  proved  very  serviceable.  First  steps  in  classification  may  be  illus- 
trated with  other  insects  as  well  as  with  butterflies,  perhaps  better  with 
some  others.  The  teacher  will  probably  find 'this  method  most  service- 
able when  applied  in  the  group  with  which  he  is  best  acquainted.  In 
applying  the  method  to  butterflies,  the  groups  as  laid  out  in  the  works 
most  commonly  found  in  school  libraries  have  been  recognized  here  as 
sufficiently  answering  the  purpose  of  this  lesson.  Recent  changes  and 
improvements  in  the  classification  of  butterflies  may  be  introduced  when 
they  have  made  their  way  into  available  literature- 


102  INSECTS. 

The  Species.  —  Select  two  of  the  large  swallow-tail  but- 
terflies (the  large  black  ones  with  tailed  hind  wings)  that 
differ  plainly  in  coloration,  markings,  outline,  etc.  These 
are  two  different  species.  Find  out  all  you  can  about  the 
two  species,  first  by  studying  them,  and  afterward  by  read- 
ing about  them  (you  will  find  them  described  in  French's 
44  Butterflies  of  the  Eastern  United  States"),  and  note 
the  kind  of  differences  between  them  :  — 

1.  Differences  of  color  and   markings  throughout   all 
stages,  —  very  obvious  differences,  but  not  alone  sufficient 
for  distinguishing  species,  for  color  is  a  very  variable  and 
somewhat  unreliable  characteristic. 

2.  Slight  differences  in  outline,  in  external  ornamenta- 
tion, etc. 

3.  Differences  in  size. 

4.  Differences  in  habits. 

5.  Differences  in  food  of  larvse. 

6.  Differences  in  egg,  larval,  and  pupal  periods,  etc. 
Such  minor  differences  as  these  are  the  ones  commonly 

used  for  distinguishing  species.     Make  a  list  of  the  points 
that  distinguish  the  two  species  selected. 

Get  the  two  common  kinds  of  cabbage  butterflies.  The 
most  prominent  mark,  within  the  border  of  the  fore  wings, 
is  in  one  a  black  spot,  and  in  the  other  a  black  dash. 
Compare  these,  and  observe  that  the  differences  are  of  the 
same  kind  as  before.  These  are  two  species. 

The  Genus. — Now  compare  a  swallow-tail  with  a  cab- 
bage butterfly.  Note  that  while  the  two  are  alike  in  the 
possession  of  relatively  broad  wings  and  slender  bodies, 
and  in  having  six  fully  developed  feet,  their  differences 
are  yet  greater  than  those  which  distinguish  species. 
Note  the  differences  :  — 

1.  In  the  shape  of  the  hind  wings. 

2.  In  their  position  in  relation  to  the  abdomen. 


A  LESSON  IN  CLASSIFICATION.  103 

3.  In  the  structure  of  the  second  segment  of  the  body 
of  the  larvae,  etc. 

Such  differences  are  used  to  distinguish  genera.  The 
swallow-tails  belong  to  one  genus,  the  genus  Papilio  ;  and 
the  cabbage  butterflies  to  another,  to  the  genus  Pieris. 
Make  a  list  of  the  characters  which  distinguish  these  two 
genera. 

Every  species  has  two  names,  —  the  name  of  the  genus 
to  which  it  belongs,  and  its  own  specific  name.  A  man  has 
two  names,  —  a  surname  and  a  given  name.  The  surname 
corresponds  to  the  name  of  the  genus ;  the  other,  to  the 
name  of  the  species.  Just  as  there  may  be  several  John- 
sons (John,  Henry,  and  Eleazar),  so  there  may  be  several 
Papilios,  — Papilio  asterias,  Papilio  troilus,  Papilio  turnus, 
etc.  The  surname  serves  to  locate  the  man  among  the 
Johnsons  ;  the  generic  name  Papilio  locates  the  butterfly 
among  the  swallow-tails.  And  just  as  the  name  John 
tells  which  Johnson  is  meant,  so  the  name  asterias  tells 
which  Papilio  is  meant.  Observe  that  the  names  are 
written,  as  men's  names  are  written  in  a  directory,  sur- 
name first.  Which  species  of  the  genus  Papilio  have  you 
had  for  comparison  ? 

The  Family.  —  Get,  for  comparison  with  these,  one  of 
the  small,  thick-set,  swift-flying  "skipper"  butterflies, 
which  rest  with  wings  thrown  backward  until  the  costal 
margins  of  the  two  pairs  are  side  by  side.  Compare  and 
observe  the  marked  difference  in  form,  —  a  difference 
of  the  kind  used  to  distinguish  families.  This  skipper 
butterfly  is  not  only  of  a  distinct  species  and  genus,  but 
its  diverse  form  shows  a  relationship  still  more  remote. 
It  is  of  a  different  family,  the  family  Ifesperidce.  The 
genera  Papilio  and  Pieris  are  members  of  the  family 
Papilionidce.  Make  a  list  of  the  characters  which  dis- 
tinguish these  two  families. 


104  INSECTS. 

The  large,  red-brown  milkweed  butterfly,  with  dark 
markings  along  the  veins,  is  of  the  family  Nymplialidce. 
Compare  it  with  a  representative  of  each  of  the  two  other 
families  mentioned. 

Notice  that  all  the  names  of  families  end  in  -idee. 

The  Order.  — Note  that  the  smallest  group  among  ani- 
mals is  the  species,  and  comprises  those  animals  which  are 
essentially  alike.  Note  that  as  species  are  put  together  to 
form  a  genus,  so  genera  are  put  together  to  form  a  family. 
Families,  in  like  manner,  make  up  an  order.  The  three 
families  mentioned,  together  with  several  other  families 
of  butterflies  and  moths,  comprise  the  order  Lepidoptera 
(or  scale-winged  insects).  The  names  of  orders  usually 
end  in  a. 

This  grouping  of  animals  is  called  classification. 

Note  that  all  groups  are  founded  upon  certain  likenesses 
in  structure  and  development.  A  system  of  classification, 
therefore,  expresses  the  structural  and  developmental  rela- 
tionships which  exist  between  animals. 

Seven  of  the  orders  of  insects  have  been  studied  in  a 
few  of  their  representatives.  Write  the  names  of  these 
orders  in  a  column,  and  opposite  each  write  the  characters 
peculiar  to  that  order.  Your  list  should  approximately 
define  these  orders. 

Then  make  a  list  of  the  characters  which  all  these  have 
in  common.1  Your  list  should  characterize  approximately 
the  group  Hexapoda  (or  insects  proper). 

1  If  there  be  time  enough,  each  student  so  disposed  should  select,  with 
the  advice  of  the  instructor,  some  small  group  of  insects  for  a  little  special 
study,  —  some  genus  which  offers  a  number  of  local  species,  and  one  the 
metamorphoses  of  which  can  be  followed  through  in  reasonably  short 
time,  and  one  for  which  systematic  works  that  will  enable  him  to  identify 
the  species  are  at  hand.  If  undertaken  at  all,  the  group  should  be  studied 
as  thoroughly  as  possible,  especially  as  to  its  metamorphosis,  and  its 
place  in  the  economy  of  nature  and  of  man.  Full  notes  should  be  made 
of  the  things  observed  during  this  study;  and  at  its  close  an  account 


THE    SPIDER.  105 

ARACHNID    INSECTS. 
THE    SPIDER. 

Haunts. — This  much-maligned  insect  is  a  very  inter- 
esting one  when  we  come  to  study  its  habits  and  the  won- 
derful silken  web  it  spins.  Because  it  bites  sometimes 
in  self-defense,  and  because  it  sometimes  spins  its  web 
where  a  web  is  not  wanted,  it  is  very  generally  hated. 
But  its  bite  is  seldom  serious  to  human 
flesh,  and  may  be  avoided  by  simply 
avoiding  handling  the  live  spider. 
And  its  web  (out  of  doors)  is  a  thing 
of  beauty. 

No  one  needs  to  be  told  where  to 
find  spiders  in  warm  weather,  for  they 
are  everywhere  abundant.  The  largest 
ones  are  best  for  a  first  examination. 
The  spiders  which  spin  their  rich  geo- 

j_   •      1         i       •       ,  i  .  -,  SPIDER    (Semidiaerram- 

metncal  webs  in  the  spaces  in  garden  matic) .  a>  abdomen; 
fences  or  in  tangled  shrubbery,  or  the  c»  cepnaiothorax ;  p, 
ones  which  spin  their  calla-shaped 
webs  on  the  ground,  spreading  the  free  border  out  over 
the  grass  at  the  edge  of  a  sidewalk  or  beside  the  founda- 
tions of  buildings,  or  the  fleet-footed  spiders  common  in 

should  be  written  of  the  genus,  stating  all  the  points  of  structure,  haunts, 
habits,  economy,  and  development,  which  all  its  local  species  have  in 
common.     This  should  be  concluded  with  descriptions  of  each  of  the 
species,  for  which  the  following  outline  is  suggested :  — 
I.    Names  (scientific,  common) . 
II.   Measurements  (length,  extent  of  wings,  etc.). 

III.  Structure  (points  not  already  stated  in  the  account  of  the  genus). 

IV.  Coloration  (a  detailed  description). 
V.    Haunts  and  habits. 

VI.   Preparatory  stages  (a  full  account).   There  is  yet  room  for  pioneer 

work  in  this  line. 
VII.   Economic  importance  of  the  species. 


106  INSECTS. 

long  grass,  which  lay  no  snares  at  all,  but  catch  their  prey 
in  a  fair  chase,  will  serve  well  for  study.  There  is  a 
large  and  gayly  colored  spider  very  abundant  sometimes 
in  stubble  fields,  and  often  the  one  most  easily  obtainable 
for  class  use.  It  spins  a  small  geometrical  web  between 
the  Aveeds  that  overtop  the  stubble;  and  when  its  web  is 
jarred  by  the  shaking  of  the  weeds,  it  drops  to  the  ground, 
and  feigns  death.  It  may  then  be  picked  up  with  forceps, 
and  dropped  into  a  cyanide  bottle  or  into  alcohol. 

In  winter,  spiders  may  be  found  under  the  bark  of  dead 
trees,  or  aquatic  species  may  be  taken  with  a  net  among 
the  green,  submerged  plants  that  grow  on  the  borders  of 
brooks  and  ponds.  But  in  winter  there  will  be  scant 
opportunities  for  observing  their  habits  or  their  webs. 

Specimens  are  best  preserved  in  alcohol. 

Habits.  —  Observations  on  the  habits  of  spiders  are  best 
made  while  out  collecting.  The  following  are  but  meager 
suggestions  of  what  may  be  done  in  field  study. 

1.  To  see  how  its  silk  is  spun,  pick  up  a  live  spider  by 
a  hind  leg  with  forceps,  and  watch  for  the  formation  of  a 
thread  from  some  blunt  protuberances  (spinnerets)  beneath 
and  near  the  posterior  end  of  the  abdomen.     Draw  this 
thread  out  with  a  pencil,  and  observe  that  it  is  composed 
of   separate  strands.     Put  at  least  one  spinning  spider 
into  a  vial  or  pill  box,  and  take  it  home  alive. 

2.  Various  methods  of  spinning  may  be  easily  observed. 
Certain  small  spiders  will   be   seen   aimlessly  trailing  a 
thread  after  them  as  they  run  about  over  the  grass  or 
fences,  making,  not  a  web,  but  a  tangle  of  threads ;  but 
those  that  make  webs  of  artistic  patterns  have  a  uniform 
and  very  curious  method  of  procedure,  easily  seen  where 
such  spiders  are  abundant. 

3.  On  a  hot  afternoon  certain  very  small  spiders  may 
be   seen   floating   in   mid-air    upon  a  few   gossamer-like 


THE   SPIDER.  107 

threads.  This  spider  climbs  to  the  top  of  some  pile  of 
boards  or  of  brick,  on  which  the  sun  has  been  shining 
until  a  current  of  hot  air  is  arising  from  it,  elevates  its 
spinnerets,  and  starts  a  thread,  which  is  caught  up  by 
the  rising  current  of  air,  and  drawn  out  to  a  length  suffi- 
cient, by  its  buoyancy,  to  support  the  weight  of  the  spider. 
The  spider  then  lets  go  of  earth,  and  sails  away. 

4.  Of  webs,  and  especially  of  those  in  which  the  spiders 
spend  most  of  their  time,  the  shape,  position,  location, 
and  construction  should  be  noted.     A  pair  of  spiders  will 
often  be  found  on  different  parts  of  one  web.     The  male  is 
usually  much  smaller  than  the  female.     Of  flat  webs  not 
placed  vertically,  it  should  be  observed  whether  the  spider 
walks  on  the  upper,  or  on  the  lower,  side  of  the  web.     It 
should  be  noted  that  the  webs  which  show  the  greatest 
skill  in  their  construction  are  made  of  the  fewest  threads. 

5.  That  the  web  is  a  snare  for  capturing  prey,  must 
not  be  forgotten.     Note  the  position  of  the  spider  on  its 
web  while  waiting  for  its  prey.     Throw  a  small  grass- 
hopper nymph  against  the  web,  and  watch  the  spider's 
method  of  securing  its  prey.     Examine  such  insects  as 
you  find  entangled  in  webs,  and  note  whether  they  are 
dead  or  alive.     Note  the  kinds  of  insects  you  find  snared 
by  spiders. 

6.  Examine  such  old  and  tattered  webs  as   you   find 
clinging  to  fences,  and  to  rafters  in  attics,  for  the  exuviae 
of  young  spiders.     These  skins  will  show  the  close  resem- 
blance in  form  of  young  and  adult. 

7.  The  eggs  of  most  spiders  are  inclosed  in  a  round 
silken  capsule  which  is  hidden  beneath  the  bark  of  posts 
and  logs,  or  buried  among  rubbish,  or,  in  a  few  species, 
carried  about  by  the  mother  attached  to  her  spinnerets. 
It  is  often  a  third  of  an  inch  in  diameter,  and  of  a  gray- 
ish or  dirty  yellowish  color.     Within  it  the  young  ones 
are  hatched,  and  live  for  a  time  by  eating  one  another. 


108  INSECTS. 

Structure.  —  Observe  that  the  body  is  divided  into  two 
regions.  The  anterior  one  is  the  cephalothorax.  As  the 
name  indicates,  it  corresponds  to  both  head  and  thorax 
of  insects  proper.  The  posterior  region  is  the  abdomen. 
Observe  the  relative  size  and  shape  of  the  two  divisions, 
and  on  the  lower  side  of  the  body  find  the  pedicel  con- 
necting them. 

I.  Cephalothorax.  —  On  the  anterior  prominence  of  the 
cephalothorax  find  the  eyes.     With  a  lens  make  out  their 
number,  kind,  and  arrangement. 

Examine  the  two  large  mandibles  that  hang  down  from 
the  front  of  the  cephalothorax,  attached  above,  and  free 
below.  Study  their  action.  Find  a  strong,  incurved 
poison  fang  at  the  lower  end  of  each.  These  fangs  are 
hollow,  and  into  the  wounds  they  make  is  poured  a  poison 
secreted  by  glands  situated  in  the  bases  of  the  mandibles. 

Observe  (from  below)  a  pair  of  jointed  maxillary  palpi 
arising  behind  the  mandibles,  and  extending  forward, 
appearing  like  a  pair  of  dwarfed  legs.  Observe  that  their 
basal  segments  are  movable  upon  each  other,  and  closely 
surround  the  mouth.  These,  by  rubbing  together,  assist 
in  comminuting  food,  and  are  called  maxillae.  Find,  in 
all,  six  segments  in  each  palpus. 

Find  eight  legs,  and  in  each  one  seven  segments.  Ob- 
serve the  size  and  arrangement  and  action  of  the  legs. 

Examine  the  terminal  segment  to  discover  by  what  means 
the  spider  is  able  to  run  easily  over  webs  which  hopelessly 
entangle  other  insects.  Find  two  pectinated  claws,  and 
(sometimes)  a  third,  which  fits,  forceps-like,  against  them. 

II.  Abdomen.  —  On  the  under  side,  just  behind  the  hind- 
most pair  of  legs,  and  on  either  side  of  the  median  ventral 
line,  find  two  smooth,  hard  patches  covering  the  openings 
to  a  pair  of  breathing  organs.     Each  breathing  organ  is  a 
sort  of  rudimentary  lung,  through  the  leaves  of  which  the 
blood  flows  for  aeration. 


THE   CHILOPOD   OR   CENTERED,  109 

On  the  median  line,  usually  a  little  farther  back,  are 
the  openings  of  the  reproductive  organs. 

Near  the  posterior  end  are  the  spinnerets,  usually  three 
pairs  of  blunt  protuberances,  each  of  which,  when  magni- 
fied, appears  to  be  covered  with  hollow,  jointed  hairs. 
Through  these  tubular  hairs  a  fluid  substance,  secreted 
by  glands  within  the  abdomen,  is  exuded ;  and  the  fluid 
is  of  such  a  nature  that  it  immediately  hardens  on  expo- 
sure to  the  air.  When  the  spider  spins  its  web,  it  simply 
exudes  this  fluid  through  the  hundreds  of  openings ;  and 
the  liquid  streams,  uniting  and  hardening,  form  a  silken 
cord  of  very  many  delicate  strands.  A  good  way  to  see 
these  strands  is  to  allow  a  live  spider,  brought  in  from 
the  field,  to  attach  its  web,  when  it  begins  spinning,  to 
the  middle  of  a  glass  slip,  and  then  to  examine  the  point 
of  attachment  under  the  microscope. 

Development.  — The  development  of  the  spider  cannot 
well  be  traced  in  the  time  allotted  to  a  beginning  course 
in  zoology;  suffice  it,  therefore,  to  say,  that  the  young 
spider,  which  hatches  from  the  egg  and  molts  a  number 
of  times  in  coming  to  maturity,  shows  much  resemblance 
to  the  adult  in  both  form  and  habits.  Its  palpi  are  pro- 
portionately longer,  more  closely  resembling  true  legs, 
of  which  they  are  modifications. 


MYRIAPOD   INSECTS. 
THE  CHILOPOD  OR  CENTIPED. 

Haunts  and  Habits.  —  Overturn  boards,  logs,  or  stones 
that  have  been  lying  on  the  ground  for  a  long  time  in  one 
place,  and  you  will  find  beneath  them  often  numbers  of 
elongated,  wingless  insects,  of  a  brownish  color,  with  linear 
bodies  and  numerous  laterallv  extended  feet.  Find  speci- 


110 


INSECTS. 


mens  with  long  antennae  and  stout  feet,  mostly  a  single 
pair  to  each  body  segment.  These  are  popularly  known 
as  centipeds.  They  may  be  picked  up  with  forceps  and 
put  into  the  cyanide  bottle. 

The  seclusive  and  predatory  habits  of  the  live  chilopod 
should  be  studied,  and  also  the  use  of  its  antennae,  and 
the  order  of  moving  its  feet  in  walking. 

Thousand-legs  will  be  found  in  similar  situations,  distin- 
guishable by  its  smaller  size,  shorter  antennae,  two  pairs 
of  legs  (apparently)  to  each  segment,  and  by  its  disposi- 
tion to  curl  up  when  touched.  Specimens  should  be  col- 
lected for  comparison. 

External  Features.  —  Write  a  description  of  the  chilo- 
pod which  shall  embody  the  answers  to  the  following 
questions :  — 

1.  How  is  the  body  divided  into 
regions,  as  compared  with  other  in- 
sects ? 

2.  How  many  segments   in   the 
body? 

3.  How  many  eyes  are  there,  and 
of  what  sort  ? 

4.  What  is  the  shape  of  an  an- 
tenna, and  how  many  segments  in  it  ? 

5.  How  many  appendages  has  the 
first  segment  back  of  the  head,  and 
of  what  sort  ? 

6.  Where  are   the   poison   fangs 
situated  ? 

7.  Of    what    character    are    the 
mandibles  ? 

8.  Why  are  not  the  legs  underneath  the  body  ? 

9.  What  adaptations  do  you  discover  of  the  shape  and 
structure  of  the  body  to  the  life  the  insect  leads  ? 


CHILOPOD  OR  CENTIPED 
(X2). 


CRUSTACEANS. 

THE  CRAWFISH. 

(Cambarus.) 

Haunts.  — In  warm  weather  this  animal  may  be  found 
crawling  upon  the  bottom  of  brooks  and  natural  ponds. 
The  largest  specimens  will  be  found  in  creeks  and  in 
ponds  which  are  not  dried  out  in  summer.  A  water  net 
will  be  of  service  in  securing  specimens.  Large  specimens 
may  often  be  obtained  in  abundance  under  rocks  in  shallow 


CRAWFISH,  natural  size  (after  Morse). 

rapids  of  creeks.  A  bright  light  on  the  bank  of  a  creek 
at  night  will  attract  many  to  the  edge  of  the  water,  where 
they  may  be  taken  with  a  dip  net.  This  is  perhaps  the 
easiest  way  to  obtain  a  supply.  It  requires  only  a  little 
waiting  and  careful  watching.  The  light  should  be  so 
placed,  that,  as  it  shines  down  into  the  water,  the  bottom 
is  visible.  Different  species  will  be  found  in  different 

111 


112  CRUSTACEANS. 

situations.  Some  live  in  holes  in  the  soil ;  others  do  not. 
Some  of  the  former  build  chimneys  of  mud  about  the 
entrance  to  their  holes  ;  others  do  not.  Some  live  at  the 
surface  of  ponds,  on  the  floating  or  submerged  leaves  of 
aquatic  plants. 

In  many  localities  throughout  the  interior  the  species 
that  live  in  holes  are  very  abundant.  The  following 
questions  suggested  for  field  study  of  their  habits  may 
be  useful :  — 

1.  What  are  their  hours  of  activity  ? 

2.  At  what  depth  of  water  do  you  find  them  ? 

3.  Do  they  live  singly,  in  pairs,  or  in  communities  ? 

4.  Do  those  that  live  in  holes  make  the  holes  for  them- 
selves ?     Are   their   holes  ever  found   sheltered   beneath 
stones  and  tree  roots  ? 

5.  What  is  the  general  shape,  size,  and  direction  of 
these  holes,  and  at  what  level  do  they  terminate  below  ? 

6.  In  such  as  build  chimneys,  how  is  the  chimney  con- 
structed?    Is  the  chimney  ever  found  plugged  up  with 
mud,  except  in  very  dry  weather  ? 

7.  How  many  species  do  you  find,  and  what  are  the 
haunts  of  each  ? 

In  winter,  numbers  of  certain  species  may  often  be  found 
huddled  together  under  the  sheltering  edge  of  some  loose 
stone  in  the  bed  of  a  creek.  Where  the  holes  of  other 
species  are  common  in  the  banks  of  brooks,  they  may  be 
dug  out  when  the  ground  is  not  frozen. 

Habits. —  Live  specimens  may  be  kept  for  a  long  time 
in  any  sort  of  aquarium  supplied  with  food.  They  will 
eat  snails  and  insects  greedily,  and  will  live  on  almost  any 
kind  of  flesh. 

Startle  a  crawfish  at  rest  upon  the  mud,  and  observe  the 
cloud  it  raises  in  the  water,  behind  which  to  escape. 

Watch  a  crawfish  walking  about  in  an  aquarium,  and 


THE   CRAWFISH.  113 

see  how  many  feet  it  walks  with,  and  in  what  order  they 
are  moved. 

Startle  it  by  thrusting  a  stick  toward  its  eye,  and  see 
its  rapid  locomotion  backward.  How  is  this  effected  ? 

Observe  its  feeding  habits. 

Place  a  live  crawfish  in  a  small  dish,  and  barely  cover 
it  with  water.  Take  hold  of  its  body  with  forceps,  and 
observe  its  way  of  defending  itself. 

Observe  that  its  eyes  are  stalked  and  capable  of  pro- 
trusion outward. 

Gill  Currents.  —  Observe  that  on  each  side  of  the  body 
that  portion  of  the  hard  crust  beneath  which  the  legs  are 
attached  is  marked  off  from  the  rest  by  a  shallow  curved 
groove.  Within  the  portion  so  marked  off  at  the  base  of 
the  legs  is  the  gill  chamber,  containing  true  gills.  This 
chamber  is  open  at  both  ends  for  the  passage  of  currents 
of  water.  Determine  the  direction  of  the  currents  by 
placing  a  drop  of  ink  or  other  colored  fluid  in  the  water 
near  each  end  of  the  chamber,  and  watching  it  move. 

Study  the  structure  of  a  crawfish  which  has  been  a 
short  time  in  alcohol. 

Plan  of  Structure.  —  The  body  is  divided  into  two 
regions.  The  anterior  one  is  the  cepTialothorax ;  the 
posterior  one,  the  abdomen. 

Observe  that  the  body  is  made  up  of  a  series  of  seg- 
ments. These  segments  are  very  evident  in  the  abdo- 
men, but  not  so  plain  in  the  head  and  thorax,  where  they 
will  have  to  be  looked  for  on  the  ventral  surface.  It  will 
be  seen  that  each  pair  of  legs,  at  least,  is  attached  to  a 
single  segment,  though  no  traces  of  segments  may  be  dis- 
coverable on  the  dorsal  surface. 

Observe  that  every  distinguishable  segment,  except  the 
hindmost,  bears  on  its  lower  surface  a  pair  of  appendages, 

NEED.  ZOOL.  —  8 


114  CRUSTACKANS. 

Mild  that  these  appendages  vary  greatly  in  si/e  on  I  lie 
different  segments. 

I.  Cephalothorax.  -  -  The     hard    shell,    which    entirely 
-•(•\ci's    I  li«-    cephalothorax    in   its  normal    position,  is  tlie 
carapace.       'I 'In-,   stout  beak  extending  forward   from  the 
front  of   it,  between  the  eyes,  is  the  rostrum.     Observe 
that  the  whole  is  divided  into  portions  corresponding 

l,o  head   ;ind    thorax     by  a  shallow  n-n^'rn/  //rm>/v  lha!    runs 

transversely  across  the  top  of  the  carapace,  and  extends 
obliquely  l'or\v;ml  along  the  sides.  The  two  longitudinal 
grooves  on  the  carapace  hack  of  t  he  cervical  groove,  which 
mark  the  line  of  separation  of  the  two  gill  chambers  from 
the  thorax  proper,  have  been  noticed  already. 

II.  Abdominal  Segments.  —  Note  the  number  and  form 
of  the  abdominal  segments.     Flex  and  extend  the  abdomen, 
and  study  their  action.     Take  the  third  or  fourth  abdomi- 
nal segment  as  a  type,  and  in  it  locate  the  parts  as  named. 
The  convex  dorsal  plate  of  the  segment  is  the  notwm,  or 
teryum ;  the  projecting  plate  that  hangs  down  on  either 
Hide   like  the   eaves  of   a  roof   is   (he  //A-///-/////.;   I  he  ventral 
transverse  bar  between  the  bases  of  the  two  appendages  is 

the  sternum.  The  appendages  themselves  are  jointed,  and 
two-parted  at  the  tip. 

Observe  the  soft  membranous  parts  connecting  the  ab- 
dominal segments,  and  the  pivotal  joining  of  the  segments 
together  at  their  lateral  edges,  facilitating  the  ilexion 
and  extension  of  the  abdomen,  but  preventing  lateral 
motion. 

At  the  posterior  end  of  the  body  is  the  tail  fin,  and  its 
central  piece  is  the  terminal  segment  of  the  body,  and  the 
seventh  abdominal  segment,  called  the  telson.  It  bears  no 
appendages,  and  has  but  slight  external  resemblance  to 
the  other  body  segments,  being  much  modified  to  suit  a 
special  purpose.  The  two  pairs  of  similar  broad  flaps, 
which,  together  with  the  telson,  comprise  the  tail  fin,  are 


THE   CRAWFISH.  115 

the  specialized  two-parted  tips  of  the  appendages  of  the 
sixth  abdominal  segment. 

Dissection. — The  remaining  parts  to  he  mentioned  are 
best  seen  upon  dissection.  The  crawfish  is  best  dissected 
under  water.1  Pin  it  to  the  bottom  of  your  dissecting 
pan,  with  the  right  side  of  the  body  upward,  and  the  head 
from  you.  Fasten  one  pin  through  the  base  of  the  ros- 
trum, draw  the  body  out  full  length,  and  fasten  another 
pin  through  the  left  appendage  of  the  sixth  abdominal 
segment.  Cover  the  specimen  with  water,  dissect  slowly 
and  carefully  and  as  directed,  and  change  the  water  as 
often  as  it  becomes  cloudy. 

I.  Appendages.  —  Begin  with  the  series  of  appendages, 
and,  for  convenience  in  dissecting,  proceed  from  the  pos- 
terior end  forward.  Remove  each  appendage  of  the  right 
side  in  order,  and  be  very  careful  to  get  each  one  off 
entire.  Preserve  all  in  their  proper  order  for  drawing. 

The  absence  of  appendages  from  the  terminal  segment 
has  already  been  noted.  The  broad  finlike  character  and 
the  extension  backward  of  the  appendages  of  the  sixth 
abdominal  segment  have  also  been  noted.  The  smaller 
appendages  of  the  remaining  five  abdominal  segments  are 
extended  forward,  close  under  the  abdomen,  and  are  called 
swimmerets.  Each  consists  of  a  short  pedicel  of  two  seg- 
ments, with  a  pair  of  jointed  and  fringed  filaments  at  the 
tip.  The  swimmerets  of  the  fifth,  fourth,  and  third  ab- 
dominal segments  are  very  similar,  but  those  of  the  second 
and  first  segments .  are  reduced  and  smaller,  or  the  first 
entirely  wanting  in  the  female,  while  in  the  male  they 
are  specialized,  bent  forward  strongly  under  the  thorax, 
and  variously  forked,  hooked,  or  twisted  at  the  tip. 

The  next  five  pairs  of  appendages  are  the  legs,  and 
belong  to  the  thorax.  Before  removing  these,  it  will  be 

*  See  Appendix,  p.  283. 


116  CRUSTACEANS. 

well  to  remove  that  part  of  the  carapace  which  covers  the 
right  gill  chamber  at  their  bases.  To  do  this,  cut  through 
the  carapace  with  fine-pointed  scissors,  along  the  groove 
that  marks  the  boundary  between  the  branchial  chamber 
and  the  thorax  proper.  Begin  at  the  posterior  end  of  the 
carapace,  and  cut  forward  along  this  groove  to  the  cervi- 
cal groove,  and  obliquely  forward  to  its  anterior  end. 
Turn  down  and  break  away  the  cover  of  the  gill  chamber, 
and  expose  the  gills.  Observe  their  feathery  appearance. 
Observe  that  they  fill  the  chamber,  and  come  in  contact 
with  all  the  water  that  passes  through  it.  Move  the  legs 
backward  and  forward,  and  note  the  effect  on  the  gills. 
Observe  that  the  gills  are  arranged  in  vertical  series  cor- 
responding in  position  with  the  legs.  Observe  that  they 
are  also  arranged  in  longitudinal  series,  the  lower  series 
being  attached  to  basal  segments  of  the  legs,  and  the 
upper  series  (a  double  series)  attached  to  a  membrane 
extending  between  the  wall  of  the  thorax  and  the  legs. 

Examine  with  a  lens,  and  compare  in  structure,  the  gills 
of  one  complete  vertical  series.  Tear  a  small  gill  to  pieces 
with  needles,  under  water,  to  make  out  its  structure. 

Remove  now  each  leg,  with  its  attached  gill,  proceeding 
from  the  rear.  To  do  this,  place  a  knife  blade  between 
the  bases  of  the  leg  to  be  removed  and  the  one  in  front  of 
it,  and,  by  prying,  break  its  hard  attachments,  and  then, 
with  a  sharp  knife  or  scalpel,  cut  its  membranous  attach- 
ments. Of  the  five  pairs  of  legs,  the  first  is  used  for 
prehension  and  defense,  and  the  others  for  walking.  The 
openings  of  ducts  from  the  reproductive  organs  are  little 
pores  perforating  the  inner  angles  of  the  basal  segments 
of  a  pair  of  legs,  —  in  males,  the  fifth  or  hindmost  pair ; 
in  females,  the  third  pair. 

Having  removed  the  five  legs  of  the  right  side,  study 
the  foremost.  Note  its  great  size.  Flex  and  extend  it, 
and  study  the  structure  and  action  of  its  joints,  esDeciallv 


THE   CRAWFISH.  117 

of  the  powerful  forceps  at  its  end.  Why  are  the  blades 
of  the  forceps  roughened  on  their  inner  edges  ? 

Is  there  any  part  in  the  foremost  leg  that  is  not  present 
in  the  other  four  ? 

There  yet  remain  three  pairs  of  small  thoracic  appen- 
dages. These  are  the  maxillipeds  (or  foot  jaws).  They 
cover  the  mouth,  being  directed  forward.  The  mouth  opens 
directly  upward :  probe  between  the  maxillipeds  to  find 
it.  These  maxillipeds,  by  the  rubbing  together  of  their 
opposed  segments,  assist  in  the  comminution  of  the  food. 

Remove  the  hindmost  maxilliped,  and  compare  it  in 
structure  with  the  typical  abdominal  appendage  already 
studied.  Observe  that  it  has  a  pedicel  of  two  small  seg- 
ments, bearing  two  branches ;  that  it  has  (and  the  swim- 
meret  has  not)  a  gill  on  the  inner  side  of  the  basal  segment. 
Remove  the  second  maxilliped,  and  find  in  it  all  the  parts 
present  in  the  third. 

Remove  the  first  maxilliped,  and  find  the  same  parts 
found  in  the  other  two,  except  the  gill.  In  the  place  of 
the  gill,  there  is  a  broad  plate,  on  the  inner  side  of  its 
basal  segment.  The  vertical  series  of  gills  begins  with  the 
second  maxilliped.  Observe  that  the  second  and  first 
maxillipeds  are  much  smaller  and  softer  than  the  third. 

The  remaining  appendages  are  believed  to  belong  to 
the  head. 

Closely  following  the  maxillipeds,  and  covered  by  them, 
are  two  pairs  of  very  thin  and  delicate  maxillae.  These 
are  small,  and  closely  appressed,  and  in  removing  them 
care  must  be  taken  to  separate  them,  and  to  take  them 
with  the  forceps  by  their  basal  segment. 

Before  removing  the  maxillye,  the  gill  scoop  attached  to 
the  second  one  should  be  seen  in  place.  It  is  a  curved 
plate,  attached  to  the  outer  side  of  the  maxilla ;  it  plays 
backward  and  forward  in  the  anterior  opening  of  the  gill 
chamber,  and  by  a  sort  of  sculling  action  propels  the  water 


118  CRUSTACEANS, 

forward,  out  of  the  chamber.  Watching  it  closely,  pull 
the  maxilla  of  the  opposite  side  backward  and  forward, 
and  you  will  see  how  it  acts.  Because  it  keeps  the  water 
moving,  it  is  a  very  important  accessory  organ  of  respira- 
tion. The  water  that  bathes  the  gills  must  continually  be 
renewed,  in  order  that  sufficient  oxygen  may  be  obtained 
from  it  for  the  needs  of  the  body. 

In  front  of  the  maxillae,  find  a  pair  of  short,  hard, 
toothed  mandibles,  each  with  a  small,  three- jointed  palpus 
lying  in  a  groove  on  its  anterior  surface.  Study  the  action 
of  the  mandibles.  Find  a  thin,  leaf -like,  un  jointed  plate 
(the  metastoma),  fitting  closely  against  the  posterior  sur- 
face of  the  mandible.  This  is  not  considered  as  a  true 
serial  appendage,  but  only  as  an  outgrowth  from  the 
border  of  the  mouth. 

On  the  front  of  the  head  are  two  very  long  antennas. 
Draw  one  of  these  downward,  and  find  a  large,  basal  seg- 
ment, bearing  on  one  side  a  light-colored,  conical  process. 
In  this  process  the  duct  from  an  excretory  gland  in  the 
head  terminates.  Find,  also,  a  blade-like  branch  of  the 
antenna  beneath  the  eye.  What  is  it  there  for  ? 

The  evidently  two-forked,  short  appendages  above  the 
antennae  are  the  antennules.  Beneath  the  eye,  in  the  base 
of  each  antennule,  is  a  so-called  ear  sac. 

Compare  in  structure  an  antennule  with  an  antenna  ; 
with  a  mandible  ;  with  a  maxilla  ;  with  a  maxilliped  ; 
with  a  leg  ;  with  a  swimmeret.  Observe  that  they  all 
exhibit  modifications  of  one  type  of  structure  ;  and  the  type 
is  a  two-jointed  pedicel,  bearing  (normally)  a  pair  of 
jointed  branches.  In  the  legs,  one  of  the  branches  is 
suppressed,  and  the  other  is  enormously  developed  to  form 
the  part  of  the  leg  comprised  in  the  five  terminal  segments. 
In  all  the  thoracic  appendages,  except  the  first  and  the 
last,  there  is  an  internal  process  from  the  basal  segment, 
forming  a  gill. 


THE    CRAWFISH.  119 

Preserve  all  these  appendages  in  their  proper  order  until 
the  dissection  is  finished. 

II.  The   Eye.  —  Examine   the  eye.       Pull  •  it   outward 
with  forceps,  and  note  the  length  of  its  stalk.     Its  stalk 
is  muscular,  and  capable  of  turning  the  eye,  when  pro- 
truded, to  look  in  any  direction,  —  an  admirable  compen- 
sation for  the  stiffness  of  the  creature's  neck.     Examine 
a  section  of  its  cornea   with   low   power,  to   make    out 
whether  it  is  a  compound  eye  or  an  ocellus. 

III.  Internal    Organs.  —  Now    carefully   dissect    away 
from   the    thorax    the    wall    that  is  uppermost,  and  cut 
away  all  of  the  carapace  as  far,  at  least,  as  the  median 
dorsal  line,  taking  care   not  to   injure  any  of  the  deli- 
cate organs  that  lie   beneath.      Cut   away,  also,  all  the 
part  that  is   uppermost  of   the  notum  (tergum)  of   the 
abdomen  ;  also  the  right  pleurum. 

(1)  Organs  of  Circulation.  —  In  the  inner  wall  of  the 
branchial  chamber,  observe  the  vertical  canals  which 
convey  the  blood  from  the  gills  toward  the  heart.  These 
canals  may  sometimes  be  seen  through  the  wall  before 
dissection  of  this  part. 

The  heart  lies  in  the  top  of  the  thorax,  under  the  center 
of  the  carapace,  in  a  sort  of  membranous  inclosure  called 
the  pericardial  sinus.  AVhen  the  carapace  is  cut  away, 
beneath  it  should  be  found  the  thin,  upper  wall  of  this 
cavity.  Cut  through  this,  and  expose  the  heart,  a  thin 
transparent,  angular  sac,  suspended  normally  in  the  color- 
less blood  that  fills  the  sinus.  Find  five  small  arteries 
starting  from  its  anterior  end.  Three  of  these,  the  central 
ones,  proceed  directly  forward  toward  the  head ;  and  the 
other  two,  the  lateral  pair,  proceed  downward  and  forward 
toward  the  lobes  of  the  liver,  which  they  supply  with  blood. 
Find  a  large  artery  starting  from  the  posterior  end  of  the 
heart,  and  immediately  dividing  into  two  branches,  one 
of  which  continues  backward  along  the  upper  side  of 


120  CRUSTACEANS. 

the  abdomen,  while  the  other  turns  downward  toward  the 
ventral  surface.  All  these  arteries  convey  blood  out  from 
the  heart  directly  to  the  tissues,  through  their  many 
minute  branches.  The  blood  has  no  such  channels  for 
return,  but  finds  its  way  back  to  the  gills  by  percolating 
through  the  interspaces  of  the  tissues  and  internal  organs. 
It  comes  back,  necessarily,  laden  with  carbonic-acid  gas, 
the  product  of  oxidation  in  the  tissues,  and  must  needs 
go  to  the  gills  to  exchange  this  noxious  gas  for  a  fresh 
supply  of  oxygen.  There  is  a  passageway  for  the  blood 
up  one  side  of  the  central  supporting  portion  of  the  gill, 
and  down  the  other ;  and  to  get  from  one  into  the  other, 
the  blood  must  flow  through  very  delicate  capillary  tubes 
that  lie  out  in  the  most  delicate  gill  filaments,  and  connect 
the  two  passages.  In  passing  through  these  capillary 
tubes,  the  blood  currents  on  the  inside  of  them  are  sepa- 
rated from  the  water  currents  outside  only  by  very  thin 
membrane,  through  which  the  necessary  exchange  of  gases 
takes  place.  The  blood  is  then  returned  from  the  gills 
through  the  vertical  canals  already  noticed  in  the  thoracic 
wall,  to  the  pericardial  sinus.  It  reenters  the  heart 
through  six  apertures  which  are  guarded  by  valves  iii- 
side.  One  of  these  apertures  may  be  seen  on  each  side 
of  the  heart,  a  pair  on  its  upper  surface,  and  a  pair  on 
its  lower  surface.  Find  them,  using  a  lens.  When  the 
heart  is  filled  with  blood,  it  contracts  ;  and  the  blood, 
being  prevented  by  valves  from  flowing  back  into  the 
pericardial  sinus,  is  forced  out  through  the  arteries. 
When  the  heart  relaxes  again,  the  valves  fly  open,  and 
the  blood  from  the  sinus  rushes  in  and  fills  it,  and  is 
driven  outward  through  the  arteries  at  its  next  contrac- 
tion. The  currents  coming  up  from  the  gills  continually 
renew  the  supply  in  the  pericardial  sinus. 

Several  delicate  fibrous  bands  may  be  seen  connecting 
the  heart  with  the  walls  of  the  pericardial  sinus. 


THE  CRAWFISH.  121 

(2)  Organs  of  Reproduction.  —  The  reproductive  organs 
will  be  found  just  beneath  the  floor  of   the  pericardial 
sinus,  whitish  in  the  male,  and  with  a  pair  of  very  long 
convoluted  tubes  or  ducts  (one  on  each  side),  yellowish 
(sometimes  dark  colored  from  the  presence  of  eggs),  in 
the  female,  and  with  a  pair  of  short,  descending  ducts. 

(3)  Organs   of   Digestion.  —  Study  next  the  organs  of 
digestion,  the  alimentary  canal  and  its  appendages.    Dis- 
sect away  all  the  organs   that  cover  it.      In  doing  this-, 
observe  in  the  abdomen  a  thin  layer  of  muscle  above  the 
straight  intestine,  and  a  thick  layer  below  it.     The  upper 
muscle  extends  to  the  abdomen,  and  the  lower  flexes  it. 
What   reason  is  there  for  the  much  greater  size  of  the 
flexing  muscle  ?     Make  a  shallow  cut  along   the  median 
line  of  this  lower  muscle,  and  remove  the  upper  half  of 
it.     It  will  separate  easily,  if  taken  in  a  single  long  roll. 

A  pair  of  big  forceps,  three  pairs  of  maxillipeds,  two 
pairs  of  maxillae,  and  one  pair  of  mandibles,  have  already 
been  found  to  be  the  external  agents  for  the  communica- 
tion of  food.  The  food  passes  from  the  mouth  directly 
upward  through  a  short  esophagus,  into  a  large,  bag-like 
stomach,  which  nearly  fills  the  head  cavity,  and  extends 
backward  a  little  way  into  the  thorax.  It  is  divided  into 
two  chambers  by  a  constriction.  On  either  side  of  its 
posterior  end  are  a  pair  of  large  yellow  or  brown  glands, 
which  are  accessory  organs  of  digestion,  called  liver. 
Find  the  ducts  by  which  they  pour  their  secretions  into 
the  alimentary  canal.  Posterior  to  these  is  the  straight 
intestine. 

The  comminution  of  the  food  is  continued  in  the 
stomach,  the  internal  surface  of  which  is  armed  with 
hard  teeth  and  ossicles,  which  make  it  a  grinding  organ. 
Cut  it  open,  and  find  these  hard  parts.  The  food  passing 
out  from  the  stomach  is  mixed  with  secretions  from  the 
liver,  and  is  digested.  It  then  passes  through  the  walls 


122  CRUSTACEANS. 

of  the  intestines,  directly  into  the  blood,  and  is  ready 
for  distribution,  and  for  use  in  the  cell  construction. 

Tear  a  bit  of  liver  to  pieces  in  water  on  a  slide,  and 
examine  with  low  power  to  make  out  its  structure. 

In  the  base  of  the  head,  in  front  of  the  mouth,  are 
two  small  excretory  glands  of  light-greenish  color.  The 
ducts  from  these  open  on  the  basal  segments  of  the 
antennae,  as  already  noticed. 

IV.  Nervous   System.  —  Find    now   the   parts   of   the 
nervous  system.     On  the  floor  of  the  abdomen  a  longi- 
tudinal   chain   of   nervous   ganglia  will  be  readily  seen. 
Count  the  ganglia  of   the  abdomen.     Observe  the   deli- 
cate white  nerve  fibers  radiating  from  them. 

In  the  thorax,  the  chain  seems  to  disappear  in  a  sort  of 
canal  formed  on  the  ventral  surface  by  the  hard  plates 
arising  from  the  floor,  and  forming  a  sort  of  internal 
skeleton.  These  plates  are  for  the  attachment  of  the 
powerful  muscles  of  the  legs  and  of  the  abdomen.  By 
carefully  cutting  away  the  hard  parts  that  hide  the  nerve 
chain,  it  may  be  followed  forward  to  the  head.  A  large 
ganglion  will  be  found  just  behind  the  esophagus,  and  a 
larger  cephalic  ganglion  or  brain  will  be  found  just  behind, 
and  a  little  above,  the  bases  of  the  antennules.  These 
two  large  ganglia  are  connected  by  fibers  passing  on  either 
side  of  the  esophagus,  and  forming  the  esophagal  nerve 
collar.  From  the  cephalic  ganglion,  nerves  may  be  traced 
to  the  eyes,  antennae,  and  antennules. 

V.  Concluding   Work.  —  If  any  of   the   paired  organs 
mentioned   have   not  been  found   thus  far,  they  may  be 
looked  for  in  what  remains  of  this  dissection  (the   left 
side),  or  in  another  specimen.     Finally  remove  carefully 
the  series  of  appendages  belonging  to  the  left  side  of  the 
body. 

Gather  together  in  pairs  all  the  appendages  of  the 
body,  in  order,  as  follows :  — 


THE   CRAWFISH.  123 

One  pair  of  antennules. 

One  pair  of  antennae. 

One  pair  of  mandibles. 

Two  pairs  of  maxillae. 

Three  pairs  of  maxillipeds. 

Five  pairs  of  legs. 

Six  pairs  of  swimmerets. 

Draw  all  these  accurately  and  in  order,  twice  natural 
size.  If  the  parts  of  the  smaller  appendages  are  not 
easily  made  out,  place  such  between  two  glass  slips,  and 
examine  with  low  power  of  microscope. 

Make  a  diagrammatic  drawing  of  a  longitudinal  section 
of  the  body,  showing  the  relative  size  and  position  of  the 
principal  internal  organs. 

Make  a  drawing  of  a  crawfish  in  its  natural  position, 
as  seen  from  above. 

Serial  Homology.  —  Observe  the  striking  similarity  in 
structure  which  underlies  the  great  diversity  in  size  and 
use  in  all  the  appendages.  Similar  likeness  in  the 
arrangement  of  the  parts  of  the  segments  which  bear  the 
appendages  is  also  evident;  and  these  things,  together 
with  a  more  marked  correspondence  during  the  early 
stages  of  development,  indicate  that  each  segment  is 
homologous  with  every  other.  The  segments  being 
serially  arranged,  this  is  called  serial  Jiomology. 

Development.  —  If  crawfishes  be  collected  in  early  spring, 
the  females  will  be  found  with  large,  berry-like  clusters 
of  small,  round,  dark-colored  eggs,  glued  fast  to  the 
swimmerets.  As  these  are  lashed  backward  and  forward 
through  the  water,  the  eggs  are  continually  washed,  and 
kept  free  from  mud  and  other  impurities.  When  the 
eggs  hatch,  they  split  in  halves,  and  the  emerging  young, 
already  armed  with  well-developed  forceps,  cling  to  the 


124  CRUSTACEANS, 

swimmerets.  The  young,  when  hatched,  are  nearly  a 
quarter  of  an  inch  long,  almost  transparent,  and  in  struc- 
ture show  much  resemblance  to  the  adults.  The  points 
of  their  forceps  are  variously  hooked,  enabling  them  the 
better  to  hang  on  to  the  maternal  swimmerets.  In  the 
process  of  development,  molting  takes  place  several  times. 
The  carapace  splits  down  the  back,  and  the  animal  crawls 
out  limp  and  defenseless.  It  has  great  difficulty  in  with- 
drawing its  legs,  and  sometimes  breaks  them  off ;  but  new 
ones  will  grow  out  from  the  broken  stumps.  Specimens 
will  be  found  occasionally  with  one  forceps  smaller  than 
the  other :  the  smaller  one  is  replacing  one  that  has  been 
lost. 

The  time  of  each  molt  is  a  critical  period  in  the  life  of 
the  animal ;  for  when  its  hard  coat  of  mail  is  gone,  its 
muscles  overwrought  with  the  struggle  of  extrication,  and 
even  its  defensive  weapons  soft  and  pliant,  it  becomes  an 
easy  prey  to  even  its  weaker  enemies.  It  therefore  seeks 
the  closest  seclusion  at  such  times. 

The  exuvia  of  the  crawfish  is  not  broken  in  molting, 
except  by  the  one  longitudinal  slit ;  and  after  the  animal 
emerges,  the  edges  of  this  slit  come  together  again  elas- 
tically,  and  the  exterior  looks  much  as  it  did  before  the 
molting.  The  hard  parts  of  the  stomach  are  shed  also 
at  every  molt. 

Crawfishes  live  a  number  of  years.  They  grow  rapidly 
during  the  first  season,  after  attaining  a  length  of  an  inch 
and  a  half.  They  grow  more  slowly  in  later  years,  and 
rarely  attain  a  length  of  more  than  five  or  six  inches. 

Crawfishes  belong  to  the  group  Crustacea. 

Other  Crustaceans.  —  Two  other  very  common  crusta- 
ceans are  excellent  subjects  for  study  here,  as  they  illus- 
trate important  differences  in  crustacean  structure. 
These  are  the  Asellus  and  the  Cyclops. 


THE   ASELLUS. 


125 


THE   ASELLUS. 

Haunts.  —  This  animal  lives  amid  the  submerged  plants 
of  our  streams  and  ponds.  It  is  about  an  inch  long, 
and  of  a  uniform  slaty  gray  or  pale-brown  color.  If  plants 
be  drawn  out  of  the  water,  it  will  be  found  clinging 
to  them,  and  may  be  picked  up  with 
forceps,  and  dropped  into  alcohol  for 
preservation.  Live  specimens  should 
be  kept  in  a  glass  jar,  in  water,  with 
aquatic  plants,  in  order  that  their 
feeding  habits  and  method  of  getting 
about  may  be  studied. 

External  Features.  —  Place  a  live 
asellus  in  a  watch  crystal  with  water. 
Add  a  few  drops  of  chloroform  or 
ether.  Observe  as  to  its  general  form 
the  following  points  :  — 

1.  A  nearly  linear  body,  much  flat- 
tened dorsally. 

2.  A  distinguishable  head,  with  a 
pair  of  sessile  eyes,  and  greater  and 
lesser  antennae,  easily  seen  from  above. 

3.  A  long,  distinctly  segmented  thorax,  bearing  seven 
pairs  of  legs. 

4.  A  short,  broad  abdomen,  with  a  pair  of  terminal  sty- 
lets projecting  posteriorly. 

As  soon  as  the  animal  has  become  quiet,  place  the  watch 
glass  on  the  stand  of  the  microscope,  and  with  low  power 
(100  diameters)  focus  upon  various  parts  of  the  abdominal 
stylets.  They  are  sufficiently  transparent  to  permit  the 
blood  in  them  to  be  seen  circulating. 

Obtain  a  specimen  which  has  been  a  short  time  in  alco- 


ASELLUS. 


126 


CRUSTACEANS. 


hol,  and  examine  the  gills  (which  are  beneath  the  abdomen 
in  this  crustacean)  and  the  mouth  parts.  Then  remove 
all  the  appendages  of  the  body,  arrange  them  in  order 
in  glycerine  upon  a  slide,  cover  with  another  slide,  and 
make  a  serial  drawing  of  them  as  seen,  magnified  10  to 
25  diameters.  Make  a  larger  drawing  of  the  terminal 
segments  of  one  of  the  first  pair  of  thoracic  legs,  and 
explain  the  action  of  these  parts. 


THE    CYCLOPS. 

Haunts  and  Habits.  —  The  water  of  an  aquarium  in 
which  aquatic  plants  have  been  growing  is  almost  certain 
to  contain  this  animal.  It  is  large 
enough  to  be  seen  without  a  lens 
(about  a  twenty-fifth  of  an  inch  long). 
It  appears  as  a  white  speck  in  the 
water,  is  very  active,  and  swims  with 
a  peculiar  jerky  movement.  Each 
large  female  cyclops  will  usually  carry 
a  pair  of  egg  sacs  attached  at  the  sides 
of  the  abdomen. 
* 

External  Features.  —  Take  up  half 
a  dozen  such  specimens  with  a  drop- 
ping tube,  place  them  in  a  watch  glass 
with  water,  and  add  a  little  ether. 
Place  them  under  the  miscroscope, 
and,  having  found  one  that  presents  a 
good  dorsal  view,  study  it  with  low 
power,  to  make  out  the  following  points  as  to  its  general 
form  :  — 

1.  An  oval  body,  tapering  posteriorly. 

2.  A  dome-shaped  carapace,  covering  the  front  of  the 


CYCLOPS  (X120). 


FURTHER   CLASSIFICATION.  127 

cephalothorax,  followed  by  four  free  thoracic  segments  of 
gradually  decreasing  width. 

3.  A  tapering  abdomen  terminated  by  a  pair  of  long, 
bifurcated  stylets. 

4.  A  pair  of  relatively  large  egg  sacs  attached  to  the 
first  of  the  four  apparent  abdominal  segments.     This  first 
segment  is  really  composed  of  two  segments  which  have 
grown  together  in  the  development  of   the  female,  but 
which  remain  distinct  in  the  male  (see  cut). 

On  the  extreme  front  of  the  carapace  find  a  pair  of  eyes 
so  close  together  that  they  appear  as  one  under  low  power. 

At  the  front  find  also  two  long,  conspicuous  first  an- 
tennce,  and  just  beneath  them  a  pair  of  small  second  antennce. 

The  remaining  appendages  may  be  seen  in  a  ventral 
view  of  the  animal.  They  are  a  pair  of  blunt,  dark- 
colored  mandibles,  and  two  pairs  of  bristling  maxillce, 
surrounding  the  mouth,  and  some  distance  behind  these 
five  pairs  of  thoracic  appendages  (legs),  the  fifth  pair 
rudimentary. 

Note  the  absence  of  breathing  organs.  Respiration 
takes  place  through  the  skin.1 


FURTHER    CLASSIFICATION. 

We  have  illustrated,  by  examples,  species,  genera,  fam- 
ilies, and  orders,  among  animals.  We  have  said  that  the 
species  is  the  smallest  zoological  group,  and  comprises 
animals  that  are  essentially  alike.  We  have  combined 
related  species  into  a  genus,  related  genera  into  a  family, 
and  related  families  into  an  order.  And  now  we  have 
extended  our  study  far  enough  to  have  material  for  illus- 
trating the  higher  groups.  Orders  are  in  the  same  way 

1  Read  "Anatomy  and  Metamorphosis  of  Cyclops,"  in  Brooks's  Hand- 
book of  Invertebrate  Zoology. 


128  CRUSTACEANS. 

combined  into  classes.  The  centiped,  spider,  and  all 
the  orders  of  six-footed  insects  already  studied,  belong  to 
the  class  Insecta.  Make  a  list  of  the  characters  which  all 
these  have  in  common.  This  will  approximately  charac- 
terize the  class. 

The  crawfish,  asellus,  and  cyclops  represent  separate 
orders,  which  are  included  in  another  class,  the  class  Crus- 
tacea. Make  a  list  of  the  characters  these  have  in  common. 

Classes  are  in  like  manner  combined  to  form  branches. 
Thus  the  two  classes,  Insects  and  Crustaceans,  constitute 
the  branch  Arthropoda  (or  jointed-footed  animals). 

Branches  are  the  primary  divisions  of  the  animal 
kingdom. 

All  animals  having  the  body  made  up  of  a  definite 
number  of  rings  or  segments  with  the  hard  parts  outer- 
most, and  with  jointed  appendages,  comprise  the  branch 
Arthropoda. 

All  arthropods  that  breathe  by  trachese  (or  tracheal 
gills)  comprise  the  class  Insecta. 

All  insects  with  scaly  wings  and  complete  metamor- 
phosis comprise  the  order  Lepidoptera,  etc. 

It  often  happens  that  the  constituent  members  of  one 
of  these  groups  show  different  degrees  of  relationship 
toward  each  other.  For  example,  in  the  class  Insecta  the 
orders  of  six-footed  insects  show  much  closer  relationship 
to  each  other  than  they  show  toward  the  orders  to  which 
the  spider  and  the  centiped  belong.  In  a  case  like  this 
it  is  convenient  to  recognize  intermediate  groups.  Accord- 
ingly all  the  orders  of  six-footed  insects  are  combined  into 
a  subclass,  Hexapoda;  the  spiders  are  placed  in  another 
subclass,  Arachnida;  and  the  centiped  and  thousand-legs, 
etc.,  are  placed  in  still  another,  the  subclass  Myriapoda 
(or  many-footed  insects).  So  intermediate  groups,  when 
found  in  nature,  may  be  interpolated  between  any  of  the 
other  groups. 


FURTHER   CLASSIFICATION.  129 

Do  not  fail  to  learn  that  these  groupings  are  but  the 
result  of  an  attempt  to  represent  systematically  the  like- 
nesses and  differences  of  animals.  The  boundaries  of  the 
groups  were  but  roughly  laid  out  by  the  early  systematic 
zoologists.  They  have  had  to  be  changed  in  the  past  as 
the  structural  and  developmental  relationships  of  animals 
have  become  better  known.  They  are  changing  now,  and 
are  liable  to  further  change  with  increasing  knowledge  in 
the  future.  Any  proposed  system  of  classification,  to  be 
acceptable,  must  be  natural;  i.e.,  founded  on  existing 
important  relationships. 

NEED.   ZOOL.  9 


WORMS. 

THE   EARTHWORM. 

(Lumbricus.) 

Haunts  and  Habits.  —  This  animal  is  familiar  enough  to 
the  man  who  tills  the  soil,  and  to  the  boy  who  goes  fishing 
and  digs  his  own  bait.  It  is  common  in  garden  soil  every- 
where. It  is  strictly  nocturnal  in  its  habits.  In  warm 
weather  it  may  be  observed,  with  the  aid  of  a  lantern  at 
night,  extending  itself  from  its  burrow,  and  searching  the 
ground  over  within  a  radius  of  its  own  length. 


.XT 

EARTHWORM  (Lumbricus  terrestris). 

It  swallows  earth  in  great  quantities,  and,  having 
extracted  from  it  whatever  organic  matter  it  contains, 
ejects  it  again  in  the  form  of  castings.  These  broken 
vermiform  castings  are  familiar  objects  to  every  observ- 
ing person,  for  there  is  hardly  a  path  in  garden  or  meadow 
that  is  not  strewn  with  them.  They  are  often  found 
abundantly,  late  in  autumn,  under  piles  of  fallen  leaves. 
The  worms  in  this  way  bring  great  quantities  of  subsoil 
to  the  surface,  and  greatly  increase  the  porosity  of  the 
soil  by  eating  holes  through  it. 

130 


THE   EARTHWORM.  131 

Specimens  for  study  may  be  obtained  by  digging,  and 
at  night  by  simply  picking  them  up  when  they  are  out 
of  their  burrows  and  extended  on  the  ground.  At  sun- 
rise they  may  be  seen  in  the  mouths  of  their  burrows,  or 
partly  extended,  not  having  retired  for  the  day.  This 
explains  why  "the  early  bird  catches  the  worm." 

Field  Study.  —  In  the  field,  observe  :  — 

1.  The  quickness  with  which   they  retreat  when  dis- 
turbed by  a  heavy  step  on  the  earth  near  their  burrow. 

2.  The  force  with  which  they  cling  to  their  burrows 
when  an  attempt  is  made  to  drag  them  forth. 

3.  Their   insensibility  to   sounds,   however   loud,  and 
their  slow  sensibility  to  light. 

4.  The  size,  direction,  and  depth  of  their  burrows. 

5.  The  plugs  found  stopping  the  mouths  of  the  bur- 
rows in  the  daytime,  the    materials   used,  and  the  skill 
shown  by  the  worms  in  their  method  of  plugging. 

In  winter,  specimens  obtained  by  digging  may  be  placed 
in  a  box,  or  large  flowerpot,  of  earth,  and  kept  in  a  warm 
place,  where  they  will  quickly  resume  activity.  They 
may  be  fed  on  bits  of  raw  meat,  preferably  fat,  of  onion, 
celery,  cabbage,  etc.,  thrown  on  the  surface  of  the  soil; 
and  when  they  are  feeding  at  night,  their  habits  may  be 
observed  with  a  lamp.  By  hiding  bits  of  food  beneath 
the  surface  of  the  soil,  the  student  may  determine  whether 
worms  have  anything  corresponding  to  the  sense  of  smell, 
enabling  them  to  find  food  with  which  they  would  not 
ordinarily  come  in  contact. 

Study  of  a  Live  Specimen.  —  Place  a  live  worm  on  a 
sheet  of  wet  paper,  and  observe  :  — 

1.    In  its  body — 

(a)  Definite  anterior  and  posterior  ends. 

(6)  Correspondence  of  right  and  left  sides  (bilateral 
symmetry). 


132  WORMS. 

(c)  The  numerous  similar  transverse  segments  compos- 
ing the  body. 

(d)  The  absence  of  appendages. 
2.    In  its  motions  — 

(a)  Rhythmic  contractions  and  corresponding  changes 
in  form  of  its  body. 

(6)   Irregular  progression  forward. 

Place  the  worm  on  a  smooth,  clean  pane  of  glass,  and 
observe,  that,  while  its  contractions  continue,  its  progres- 
sion ceases. 

Draw  the  worm  backward  across  a  finger,  to  feel  the 
minute  setae  (or  bristles)  by  means  of  which  it  holds  its 
ground  on  any  except  the  smoothest  surfaces. 

Observe  how  it  crawls  backward  when  touched  near 
the  anterior  end,  performing  reflexly  the  acts  which  under 
its  ordinary  conditions  of  life  would  carry  it  to  a  safe  re- 
treat within  its  burrow. 

Turn  it  over  on  its  back  and  observe  what  follows. 

Tap  the  paper,  or  jar  the  table,  on  which  it  lies,  and  note 
the  result. 

External  Features.  —  For  a  study  of  the  general  struc- 
ture of  the  earthworm,  use  specimens  that  have  been 
anaesthetized  with  chloroform.  Select  the  largest  speci- 
men obtainable,  and  dissect  it  under  weak  alcohol ;  but, 
before  dissecting,  observe  with  a  lens  the  following 
among  its  external  features  :  — 

1.  The  darker  color  of  the  dorsal  surface. 

2.  The  greater  length  of   the  body -segments  at  the 
tapering  anterior  end. 

3.  The  dorsal  flattening  of  the  posterior  end  of  the 
body. 

4.  The  mouth  at  the  anterior  end,  and  the  prostomium 
projecting  forward  above  it,  from  the  dorsal  side  of  the 
foremost  segment. 


THE    EARTHWORM.  133 

5.  A  swollen  region  (the  clitelluni)  between  the  thirti- 
eth and  fortieth  segments  (counted  from  the  front),  em- 
bracing several  segments. 

Find  a  pair  of  small  pores  on  opposite  sides  of  the 
median  ventral  line  of  the  fifteenth  segment,  and  another 
similar  but  smaller  pair  on  the  fourteenth  segment.  These 
are  the  external  openings  of  the  reproductive  organs. 
Two  other  pairs  of  pores  may  be  made  out,  sometimes 
with  difficulty,  on  opposite  sides  of  the  median  ventral 
line,  —  a  pair  on  the  groove  between  segments  9  and  10, 
and  another  pair  on  the  groove  between  segments  10  and 
11.  These  are  the  openings  of  the  seminal  receptacles, 
(accessory  organs  of  reproduction). 

A  row  of  pores  is  present  on  the  median  dorsal  line, 
one  at  the  anterior  edge  of  each  segment,  opening  directly 
into  the  body  cavity.  These  are  not  very  evident. 

Find  two  pairs  of  sette  (or  locomotor  bristles)  on  each 
side  of  each  segment,  —  one  pair  at  the  edge  of  the  flattened 
ventral  surface ;  the  other  a  little  higher,  on  the  side  of 
the  body.  Observe  that  these  are  arranged  in  four  longi- 
tudinal double  rows. 

Pin  the  specimen  down  for  dissection  beneath  weak 
alcohol,  with  one  pin  through  the  prostomium  only,  and 
another  through  the  last  segment,  with  the  body  slightly 
stretched  between  the  pins.  Very  great  care  will  be 
necessary  to  successfully  complete  the  following  dissec- 
tion. Cut  no  more  than  directed. 

Dissection.  —  With  thin,  sharp  scissors  make  a  shallow, 
longitudinal  cut  through  the  body  wall,  along  the  dorsal 
surface,  the  entire  length  of  the  body,  taking  care  not  to 
injure  the  organs  which  lie  beneath.  At  the  middle  of 
the  body  draw  the  edges  of  the  cut  apart,  and  observe  the 
septa  (or  partitions)  which  extend  transversely  across  the 
body  cavity.  Observe  that  these  correspond  in  position 


134  WORMS. 

with  the  depressions  between  segments  seen  on  the  exte- 
rior, and  show  internal  segmentation.  Observe  that  each 
of  the  septa  is  perforated  at  the  center  for  the  passage  of 
the  alimentary  canal  and  other  vessels.  Observe,  also, 
that  the  segmentation  of  the  body  extends  to  the  alimen- 
tary canal,  which  in  this  region  is  somewhat  expanded  in 
each  segment. 

Beginning  at  the  anterior  end,  cut  the  septa  close  to  the 
body  wall  on  each  side  down  to  the  uppermost  row  of 
setae,  and  pin  back  the  flaps,  exposing  the  internal  organs. 
Most  conspicuous  among  these  will  be  the  large-lobed, 
white  seminal  vesicles,  nearly  filling  the  body  cavity 
between  the  tenth  and  the  fifteenth  segments,  and 
the  darker-colored  alimentary  canal  extending  straight 
through  the  center  of  the  body  longitudinally. 

Find  a  dorsal  Hood  vessel  extended  along  the  upper  side 
of  the  alimentary  canal,  with  five  pairs  of  aortic  arches 
extending  downward  from  it  in  segments  7  to  11,  and 
meeting  below  the  alimentary  canal  in  the  ventral  blood 
vessel,  which  extends  backwards  longitudinally. 

I.  Organs  of  Digestion. — Beginning  at  the  posterior 
end,  lift  out  the  alimentary  canal,  carefully  dissecting  it 
free  from  the  septa,  and  avoiding  disturbing  other  organs. 
Make  out  in  the  alimentary  canal  the  following  parts :  — 

1.  A  wide  pharynx,  posterior  to  the  mouth,  with  many 
radiating  muscle  fibers  extending  from  its  walls  to  the 
outer  body  walls.     When  the  soft  margins  of  the  mouth 
are  applied  to  any  object  that  is  to  be  seized,  these  muscle 
fibers,  contracting,  dilate  the  pharynx,  creating  within  it 
a  partial  vacuum,  and  exerting  a  powerful  sucking  action 
upon  the  object  seized. 

2.  An  esophagus,  a  slender,  thin-walled  tube,  extending 
backward  from  the  pharynx. 

3.  Three  pairs  of  minute  yellowish  white  calciferous 
glands  attached  to  the  esophagus  in  segments  10  to  12. 


THE   EARTHWORM.  135 

These  secrete  a  milk-white  fluid  of  unknown  function, 
containing  carbonate  of  lime. 

4.  The  crop,  a  thin- walled  dilatation  of  the  alimentary 
canal  in  segments  15  and  16. 

5.  A  muscular  gizzard,  lined  with  membranes  elevated 
in  chitinous  ridges,  usually  occupying  segments  17  to  19. 
This  is  the  principal  organ  for  grinding  and  comminuting 
the  food. 

6.  The  remainder  of  the  alimentary  canal  is  the  intes- 
tine.    It  probably  possesses  digestive  functions  through- 
out its  length. 

II.  Organs  of  Reproduction.  —  Cut  the  alimentary  canal 
in  two  at  the  back  of  the  pharynx.  Leave  the  pharynx 
in  place,  but  remove  the  remainder  of  the  digestive  tract. 
After  it  is  lifted  out  from  between  the  lateral  lobes  of 
the  seminal  vesicles,  these  organs  will  be  fully  exposed. 
These  cover  the  male  reproductive  organs ;  and  a  pair  of 
ducts  extend  backward  from  them,  to  open  to  the  exterior 
at  the  pores  already  noticed  on  segment  15. 

The  earthworm  is  hermaphrodite,  and  ovaries  will  be 
found  (sometimes  with  difficulty)  on  the  floor  of  the 
body,  —  a  pair  of  minute,  whitish  bodies  on  either  side 
of,  and  close  to,  the  median  ventral  line  of  segment  13. 
The  disconnected  oviducts,  posterior  to  the  ovaries,  pene- 
trate the  septum  between  segments  13  and  14,  and  open 
to  the  exterior  at  the  pores  already  noticed  on  seg- 
ment 14. 

Attached  to  the  septa,  between  segments  9  and  10 
and  10  and  11,  are  two  pairs  of  minute,  whitish  sacs, 
which  open,  directly  downward.  These  are  the  seminal 
receptacles,  the  accessory  organs  of  reproduction  already 
noticed.  In  them  the  sperms  from  another  individual  are 
stored  until  the  time  when  the  eggs  are  laid ;  for,  though 
the  earthworm  is  hermaphrodite,  cross-fertilization  seems 
to  be  the  invariable  rule. 


136  WORMS. 

III.  Nervous  System.  —  Remove  the  seminal  vesicles. 
This  will  entirely  expose  the  nerve  cord  which  lies -ex- 
tended  along   the   floor   of    the    body   cavity   its   entire 
length.     Observe  the  ganglion-like  swellings  in  each  seg- 
ment.    Observe  the  nerves  given  off  from  it  to  each  seg- 
ment.    Trace  it  forward  to  the  pharynx.     Observe  that 
it  forks,  surrounds  the  pharynx,  and  unites  again  above  in 
the  cephalic  ganglion  (or  brain).     Compare  this  arrange- 
ment of  the  central  nervous  system  with  that  already  seen 
in  crustaceans  and  insects. 

IV.  Organs     of    Excretion.  —  Observe    the    segmented 
organs   (nephridia), — little,  tangled,  thread-like   bodies, 
attached  to  the  posterior  side   of  each  septum,   one  on 
each  side  of  the  body  in  each  segment.     Each  of  these 
organs  opens  to  the  exterior  by  a  minute  pore,  not  here- 
tofore noticed,  and  not  easily  discovered.     Each  opens 
internally  at  the  end  which  floats  free  within  the  body 
cavity,  by  a  minute  ciliated  orifice  (discoverable  only  by 
careful  microscopic  examination).      These  are  excretory 
organs,  and  drain  out  waste  and  worn-out  materials  from 
the  body. 

V.  The  Body  Wall. — Spread  out  the  body  wall  per- 
fectly flat,  and  pin  it  so.     Observe  its  muscular  lining. 
Note  that  the  longitudinal,  fibrous  bands  are  discontinu- 
ous, as  such,  along  the  lines  occupied  by  the  locomotor 
setae.     These  setae  are  moved  by  small  muscles  of  their 
own,  not  the  least  in  importance  in  the  animal's  mechan- 
ism.     Strip  up  some  of   the  longitudinal  muscles,  and 
observe  the  circular  ones  that  lie  beneath.     Outside  these 
is  a  layer  of  epidermis. 

VI.  The  Body  Cavity.  —  Cut  a  clean  transverse  section 
of  another  specimen  which  has  been  hardened  in  alcohol, 
using  a  very  sharp  knife  or  scalpel,  and  examine  the  cut 
end  with  a  lens.     Note  that  the  body  is  made  up  of  two 
tubes,  one  within  the  other,  —  the  inner  one,  the  diges- 


THE   EARTHWORM.  137 

tive  tract,  muscular  on  its  outside  ;  the  outer  one,  the  tube 
formed  by  the  body  wall,  muscular  on  its  inside.  Note 
that  the  body  cavity  between  these  two  is  bridged  by 
the  numerous  transverse  septa.  Compare  the  earthworm 
with  the  crawfish  and  the  grasshopper  in  respect  to  this 
structure. 

Microscopic  Examination.  —  Obtain  another  anaesthe- 
tized worm.  Insert  a  slender  pointed  pipette  through  a 
puncture  into  the  body  cavity,  and  draw  out  a  drop  of 
the  fluid  filling  that  cavity.  Place  the  drop  on  a  slide, 
cover,  and  examine  with  high  power  of  microscope  to 
discover  :  — 

1.  Chloragogue  cells,  large  and  irregular,  and  yellowish 
in  color.     These  cells  form  a  layer  surrounding  the  ali- 
mentary canal  for  a  great  part  of  its  length.     They  are 
believed  to  perform   the  functions  which  the   liver  per- 
forms in  higher  animals,  at  least  to  the  extent  of  secreting 
a  fluid  to  aid  in  the  digestion  of  food. 

2.  Amoeboid  blood  corpuscles,  so  transparent  they  may 
be  overlooked  at  the  first  glance.      These  show  pseudo- 
podia,  and,  if  kept  warm,  may  be  seen  to  be  in  action, 
like  amoeba,  whence  the  name.     It  must  be  borne  in  mind 
that  these  cells  do  not  have  an  independent  existence  like 
amoeba,  but  that  they  are  constituent  cells  of   a  many- 
celled  animal,  dependent  for  their   life   upon  conditions 
supplied  by  other  parts. 

3.  Sperms.     Lay  open  the  body  cavity.     P-uncture  one 
of  the  seminal  vesicles,  and  take  from  it  with  a  pipette  a 
drop  of  its  fluid  contents.     Mount,  cover,  and  examine  this 
with  high  power  of  microscope.     It  should  contain  many 
minute  filiform  sperms,  some  of  which  may  be  seen  actively 
swimming  about.     They  may  often  be  better  seen  (but 
not  in  motion)  after  running  a  drop  of  magenta  under 
the  cover.    » 


138  WORMS. 

Mechanical  Movements  of  Blood  Vessels.  —  The  me- 
chanical action  of  the  parts  concerned  in  nutrition  can 
best  be  understood  by  studying  them  in  a  live  worm. 
Small  specimens  can  be  found  so  nearly  transparent,  that 
the  blood  vessels  can  be  seen  from  the  outside,  and  their 
pulsations  watched  with  a  lens.  But  it  will  be  found 
more  satisfactory  to  study  these  things  in  a  large  living 
specimen  that  has  been  stilled  with  chloroform  or  ether. 
Pin  the  specimen  out  in  the  dissecting  pan  in  a  |-per-cent 
salt  solution,  as  before  directed,  and  open  it  by  a  longi- 
tudinal cut  a  little  to  one  side  of  the  median  dorsal  line. 

Expose  the  blood  vessels,  and  observe  their  contrac- 
tions. Note  that  the  contractions  pass  along  the  vessels 
in  successive  waves,  which  mark  the  course  of  the  blood 
in  them.  Their  red  color  is  due  to  the  blood  they  con- 
tain, and  the  color  of  the  blood  is  in  its  liquid  part 
(plasma),  and  not  in  its  corpuscles. 

These  and  other  contractions,  sometimes  observable  in 
the  alimentary  canal,  are  performed  by  the  automatic  action 
of  muscles  within  the  walls  of  the  organs  themselves. 
These,  contracting,  push  the  contents  forward,  much  as 
water  in  a  rubber  tube  would  be  pushed  forward  if  the 
tube  were  drawn  tightly  between  the  fingers. 

Development.  —  The  eggs  of  the  earthworm  are  laid  in 
May  or  June,  and  may  be  found  at  that  time,  a  number 
together,  inclosed  within  ovate,  tough,  yellowish  or  brown 
capsules,  in-  loose  earth,  beneath  logs  and  stones.  These 
capsules  are  formed  in  the  following  peculiar  manner : 
Certain  glands  of  the  clitellum  become  very  active  at  this 
season,  and  pour  out  on  the  surface  of  the  body  a  fluid 
which  hardens  into  a  tough  membrane,  forming  a  girdle 
about  the  body.  A  thick  jelly-like  fluid  is  retained 
within  this  girdle,  between  it  and  the  body.  The  girdle 
is  gradually  worked  forward,  toward  the  head.  When 


THE    EARTHWORM.  139 

it  passes  the  openings  of  the  oviducts  on  segment  14, 
ova  are  discharged  into  it ;  and  in  passing  segments  11 
to  9  it  receives  sperms  that  have  been  stored  in  the 
seminal  receptacles.  When  it  is  passed  off  over  the  head, 
it  closes  elastically  at  both  ends,  forming  a  capsule. 
Within  this  capsule  fertilization  takes  place,  and  the 
fertilized  ova  develop,  and  give  rise  to  little  worms, 
which  feed  upon  the  nutrient  fluid  in  which  they  float, 
until  they  are  able  to  make  their  own  way  in  the  world.1 

1  Read  Darwin's  Formation  of  Vegetable  Mould  through  the  Action  of 
Worms. 


MOLLUSKS. 

THE  RIVER   MUSSEL. 
(Unio.) 

Haunts.  —  This  animal  is  common  in  all  our  rivers  and 
small  lakes.  It  is  found  on  the  bottom,  usually  partly 
buried  in  sand  or  mud.  As  it  moves  about,  it  makes  a 
trail  through  the  mud  or  sand,  —  a  shallow  groove,  with 
abruptly  sloping  sides  ;  and,  by  observing  its  track  at 
the  edge  of  the  water,  it  may  often  be  more  easily  found. 
Occasional  specimens  may  be  picked  up  at  the  bank, 
but  usually  larger  ones  will  be  found  farther  out.  They 
may  be  raked  ashore  with  a  long-handled  garden  rake, 
or  drawn  up  with  a  long-toothed  lawn  rake  from  a  boat, 
or,  in  warm  weather,  most  rapidly  obtained  by  wading 
out  on  a  submerged  sand  bank  and  picking  them  up  by 
hand.  The  dead  and  empty  shells  strewing  the  banks 
will  be  a  guide  to  the  best  places  to  search  for  live 
specimens. 

When  a  river  is  falling  after  a  flood,  many  mussels  will 
be  found  close  to  the  banks,  and  many  others  may  be  seen 
out  on  the  banks,  where  they  have  been  left  high  and  dry 
by  the  receding  waters,  and  where  they  have  died.  This 
is  a  casualty  of  a  very  common  kind  among  the  lower 
animals. 

Specimens  collected  in  the  field  may  be  carried  home  in 
a  bucket  of  water,  and  kept  alive  in  an  aquarium  impro- 
vised from  a  tub  or  a  water-tight  box,  with  a  layer  of  sev- 

140 


THE   RIVER   MUSSEL.  141 

eral  inches  of  sand  in  the  bottom  and  several  inches  of 
water  above  the  sand.  Here  something  of  their  habits 
may  be  seen. 

Study  of  a  Live  Specimen.  —  Take  a  live  specimen  in 
hand,  and  note  :  — 

1.  That    the    animal    has    entirely    withdrawn   itself 
within  its  shell. 

2.  That   its   shell   is    composed   of   two   equal   pieces 
called  valves. 

3.  That  the  valves  are  hinged  together  at  one  side. 

4.  That   they  are  firmly  held  together  at   their  free 
margins.     Try  pulling  them  apart. 

5.  That  there  is  a  central   prominence   in  each  valve 
(the  beak  or  umbo)  near  the  hinge. 

6.  That  each  umbo  is  a  center  of  growth,  with  lines  of 
growth  arranged  concentrically  around  it. 

Now  observe  one  of  the  mussels  that  have  been  placed 
on  the  sand  in  the  aquarium,  —  one  which,  having  been 
left  for  awhile  to  itself,  has  gotten  up  on  edge  and  started 
to  travel.  Observe  :  — 

1.  That  the  hinge  is  up.     It  is  on  the  back  or  dorsal 
margin. 

2.  That  the  free  margins  of  the  valve  are  down.    They 
form  the  ventral  margin. 

3.  That  they  are  slightly  separated,  and  that  the  animal 
is  partly  extended  between  them. 

4.  The  direction  in  which  the  mussel  is  traveling.    Take 
some  measured  observations  and  compute  its  rate  of  speed. 

5.  That  the  umbones  are  nearer  the  forward  or  anterior 
end.      Looking  at  the  moving  mussel  from  behind,  the 
valve  on  the  right  hand  is  the  right  valve  ;  the  other,  the 
left  valve. 

6.  That  the  animal  moves  by  a  succession  of  pulls. 
Find  out  what  does  the  pulling. 


142  MOLLUSKS. 

7.  That  there  are  two  round  fringed  openings  at  the 
posterior  end  of  the  dorsal  margin.     These  are  the  siphon 
openings.     If  the  water  be  shalloAv  enough,  there  may  be 
seen  near  these  a  play  of  wavelets  on  the  surface,  indicat- 
ing currents.     Place  a  drop  of  india  ink  or  other  colored 
fluid  in  the  water  near  these  openings,  and  discover  the  di- 
rection of  the  currents  in  each  of  them.    Record  the  result. 

8.  That  there  is  an  exserted  membrane  fringing  the 
free  border  of  each  valve  all  around.     This  is  the  edge  of 
the  mantle.     Touch  it  in  various  places,  and  note  its  sensi- 
tiveness. 

9.  That  there  is  a  white,  flexible,  muscular  foot  pro- 
truded downward  and  forward  between  the  mantle  margins 
into  the  sand.     By  quietly  placing  a  finger  horizontally 
in  the  sand  in  front  of  the  mussel,   and  directly  in  its 
course,  and  waiting  for  the  animal  to  travel  over  it,  you 
may  discover  how  the  foot  is  used. 

Pick  up  an  active  mussel  quickly  out  of  the  water,  and 
see  how  quickly  the  foot  is  retracted. 

Place  a  sheet  of  tin  or  a  pane  of  glass  on  the  sand,  and 
lay  a  mussel  on  it  at  its  center.  Note  how  the  animal 
protrudes  and  uses  its  foot,  in  its  efforts  to  rise. 

Explain  its  inability  to  rise  on  edge  and  move  away. 

Discover  by  experiment  whether  the  fringes  of  the 
siphons  are  sensitive  to  light. 

Structure.  —  In  dissecting  a  river  mussel,  the  first  thing 
to  be  done  is  to  get  the  shell  open  so  as  to  get  at  the 
animal  so  securely  locked  inside.  The  valves  are  held 
together  by  two  stout,  transverse  muscles.  Select  a  live 
specimen  of  large  size  for  the  first  dissection.  Place  it 
for  a  few  moments  in  water  as  warm  as  the  hand  can 
bear.  This  will  relax  the  muscles.  The  valves  may  then 
be  opened  slightly,  and  a  block  inserted  between  them 
to  keep  them  so. 


THE   RIVER   MUSSEL. 


143 


Observe  a  soft,  whitish  membrane,  with  a  narrow,  dark- 
colored,  ruffled  border  lining  each  valve.  It  is  the  mantle. 
Loosen  the  edge  of  the  mantle  from  the  edge  of  one  valve 
by  pushing  a  knife  blade  between  the  two,  and  drawing 
it  entirely  around  the  free  border  of  the  valve.  Keep 
the  point  of  the  blade  close  to  the  shell.  Observe  that 
the  mantle  clings  to  the  valve  along  a  line  within  and 
parallel  to  its  margin.  Observe  that  the  point  of  the 
knife  blade  meets  with  an  obstruction  near  the  dorsal  sur- 


DIAGRAM  OF  UNIO:  u,  umbo;  h,  hinge;  s,  siphons;  small  arrows  indicate 
the  direction  of  the  water  currents;  large  arrow  indicates  direction  of 
travel,  and  also  depth  to  which  the  animal  is  usually  found  buried  in  the 
sand  in  locomotion ;  /,  foot ;  e,  edge  of  the  valves ;  I,  concentric  lines  of 
growth ;  m,  mantle  margins  extruded  in  front. 

face,  at  both  anterior  and  posterior  ends :  it  encounters 
the  strong  muscles  which  hold  the  valves  together.  Cut 
these  off  close  to  the  valve.  Notice  the  valves  spring 
apart  when  these  are  severed.  Free  the  one  valve  from 
all  connection  with  mantle  and  muscles,  and  turn  it  back 
like  the  lid  of  a  watch  case. 

I.  The  Different  Parts.  —  Study  the  following  parts, 
doing  no  more  dissecting  than  is  absolutely  necessary :  — 

1.    The  mantle.      Observe  the  thinness  and   transpar- 


144  MOLLUSKS. 

ency  of  its  inner  part,  and  the  sensitiveness  and  mobility 
of  its  border. 

Observe  that  it  consists  of  two  lobes  corresponding  in 
size  to  the  two  valves  of  the  shell,  and  that  its  border  is 
continuous  from  one  to  the  other. 

Observe  how  loosely  it  infolds  the  body,  and  covers  it 
above  and  on  the  sides. 

2.  The  siphons.     Observe  that  the  siphon  orifices  are 
formed  from  the  edge  of  the  mantle,  and  that  the  adjacent 
mantle  margins  are  grown  together  between  the  upper  and 
lower  orifices,  entirely  separating  them,  and  that  below 
the  lower  orifice  the  mantle  margins  are  free.     The  upper 
tube  leads  out  from  the  cloacal  chamber,  and  is  therefore 
called  the  cloacal  siphon.     The  lower  opening  leads  into 
the  branchial  (or  gill)  chamber,  and  is  therefore  called  the 
branchial  siphon. 

3.  The  principal  muscles.     Observe  the  severed  ends 
of  the  two  stout,  white  adductor  muscles  projecting  ver- 
tically through  the  mantle. 

Close  beside  each  of  these  find  the  end  of  a  much 
smaller,  oblique  muscle,  which  was  also  severed  in  open- 
ing the  shell.  These  two  are  the  retractor  muscles.  They 
retract  the  foot.  Prick  the  point  of  the  foot,  and  watch 
the  posterior  adductor  muscle.  Prick  the  back  part  of 
the  foot,  and  watch  the  anterior  adductor  muscle.  If 
these  were  fast  to  the  shell,  instead  of  being  drawn  down, 
they  would  draw  the  foot  up,  as  may  be  seen  later  by 
pricking  the  retractors  of  the  other  side,  near  their  origin, 
before  severing  them  from  the  valve. 

In  the  thickened  border  of  the  mantle  are  many  muscle 
fibers,  to  which  its  mobility  is  due,  and  by  which  it  was 
attached  to  the  shell  along  the  pallial  line. 

4.  The  gills.     Turn  the  loose  part  of  the  mantle  back 
upon  the  dorsal  surface,  and  expose  the  gills.     They  hang 
suspended  in  the  branchial  chamber  at  the  posterior  part 


THE   RIVER   MUSSEL.  145 

of  the  body.  Observe  that  they  are  thin,  ribbed  and  per- 
forated folds  of  membrane  extending  longitudinally  beside 
the  body,  a  pair  on  either  side.  Between  the  two  pairs 
observe  the  soft,  white,  muscular  abdomen,  extending 
downward  and  forward,  and  terminating  insensibly  in  the 
retracted  and  minutely  wrinkled  foot. 

Examine  the  surface  of  the  gills  with  a  lens. 

Lift  with  forceps  the  lower  edge  of  one  of  the  gills  (if 
the  outer  gill  appear  dark  and  distended,  lift  the  inner 
one),  stick  a  sharp  knife  or  scalpel  through  it,  and  make 
a  vertical  slit  out  to  the  edge.  Then  look  at  the  cut  edge 
of  the  piece  held  in  the  forceps,  and  see  that  the  gill 
membrane  is  double  and  V-shaped  in  cross  section,  and  is 
suspended  by  the  arms  of  the  V  from  above.  Insert  the 
point  of  a  knife  blade  into  the  end  of  the  piece  held  in  the 
forceps,  and  split  it  lengthwise.  Then  take  a  small  piece 
of  the  single  gill  membrane  thus  obtained,  and  mount,  and 
examine  it  (without  cover  glass)  with  low  power.  Note 
the  shape  and  arrangement  of  the  openings  in  the  mem- 
brane, the  location  and  action  of  the  cilia. 

Pass  a  bristle  or  other  probe  into  the  cloacal  chamber 
from  its  siphonal  orifice.  Observe  that  this  chamber  lies 
entirely  above  the  gills,  and  that  it  has  no  communication 
with  the  branchial  chamber  below,  except  through  the  gills. 

Lay  open  the  cloacal  chamber  for  half  an  inch  by  a 
single  cut  with  scissors  through  the  wall  of  the  cloacal 
siphon.  Observe  the  minute  openings  leading  from  the 
floor  of  the  cloacal  chamber  down  into  the  gills.  Pass 
a  bristle  into  one  of  these,  and  observe  that  it  ends  blindly 
at  the  lower  edge  of  the  gill. 

Make  a  short  longitudinal  cut  through  the  posterior 
part  of  the  attachment  of  both  gills  to  the  cloacal  cham- 
ber. Then  lift  with  forceps  the  cut  edge  of  the  outer 
layer  of  the  outer  gill,  and  observe  the  numerous  septa 
or  partitions  extending  transversely  between  the  outer 

NEED.  ZOOL.  —  10 


146  MOLLUSKS. 

and  the  inner  layers,  connecting  the  arms  of  the  V. 
Observe  also  that  the  inner  layer  of  the  outer  gill  is 
continuous  with  the  outer  layer  of  the  inner  gill. 

Having  already  observed  that  the  water  passes  in  at 
the  branchial  and  out  at  the  cloacal  siphon,  give  now  an 
explanation  of  the  course  it  takes,  and  of  the  manner  in 
which  it  is  propelled  onward  in  its  course. 

5.  The  blood  vessels.  Turn  the  free  lobe  of  the  mantle 
down  again,  and  loosen  the  dorsal  portion  from  both 
valves.  Then  pull  downward  gently  on  the  free  lobe  so 
as  to  bring  the  dorsal  aspect  of  the  body  better  into  view. 
The  dorsal  portion  of  the  mantle  is  very  thin  and  trans- 
parent, and  through  it  may  be  seen,  in  the  part  that  was 
directly  beneath  the  hinge,  an  oval  or  elongated  trans- 
parent vessel  regularly  but  slowly  pulsating.  This  is  the 
ventricle.  Pinch  up  the  mantle  with  forceps,  and  cut  it 
away  from  this  region,  and  the  parts  will  be  better  seen. 
The  blood  comes  to  the  ventricle  from  a  pair  of  auricles 
located  one  on  either  side.  Each  auricle  lies  directly 
between  the  gills  and  the  ventricle,  and  is  somewhat  coni- 
cal in  form,  with  the  apex  of  the  cone  toward  the  ventri- 
cle. A  branchial  vein  brings  the  blood  from  the  gills  to 
the  lower  end  of  the  auricle.  The  ventricle  is  emptied 
principally  through  a  pedal  artery  which  curves  forward 
and  downward  toward  the  foot. 

Observe  that  the  dark-colored  intestine  runs  directly 
through  the  ventricle,  like  a  draught  pipe  through  a  loco- 
motive boiler,  there  being  no  open  communication  between 
the  two  vessels. 

Observe  the  pulsations  of  the  heart.1     First  the  auricle 

1  A  very  satisfactory  demonstration  of  the  action  of  the  heart  may  be 
made  by  cutting  away  with  bone  snips  the  portion  of  the  shell  which 
immediately  surrounds  the  hinge,  and  covers  the  heart,  leaving  the  ani- 
mal intact  within.  A  thin-shelled  specimen  should  be  selected  for  this. 
If  kept  under  water,  or,  better,  under  f-per-cent  salt  solution,  the  pulsa- 
tions may  be  observed  for  a  long  time. 


THE   RIVER   MUSSEL.  147 

swells  up  with  limpid  transparent  blood  from  the  gills, 
and  then  it  contracts  and  fills  the  ventricle,  which  then 
contracts  in  turn,  sending  the  blood  out  through  the  pedal 
artery. 

II.  Digestive   System.  —  On  either   side   of   the  front 
part  of  the  abdomen  observe  two  soft  triangular  flaps 
narrowing  toward  the  front.     These  are  the  labial  palps. 
Between  them,  directly   in   front,  is   the  mouth,  which 
leads  through  a  short  esophagus  into  the  stomach.     The 
stomach   is   surrounded   by   a   dark   brown   mass   called 
liver,  easily  seen  when  the  mantle  is  removed.     The  course 
of  the  digestive  tract  is  difficult  to  trace  in  a  fresh  speci- 
men, but  may  be  followed  more  readily  in  one  that  has 
been  hardened  in  alcohol.     Posterior  to  the  stomach  there 
are  several  turns  of  the  intestine l  before  it  emerges  from 
the  abdomen  to  pass  into  and  through   the  pericardial 
cavity,  where  it  has  already  been  noticed  running  through 
the  ventricle.     It  terminates  in  the  cloacal  chamber.     If 
the  heart  and  the  part  of  the  intestine  posterior  to  the 
abdomen  be  removed,  two  dark-colored  renal  organs  will 
be  seen  below  them.     These  organs  open  below  into  the 
cloacal  chamber,  and  above  into  the   pericardial  cavity, 
thus  connecting  the  body  cavity  with  the  exterior,  as  do 
the  renal  (segmental)  organs  in  the  earthworm. 

III.  Nervous  System.  —  This  will  be  studied  with  ex- 
treme  difficulty  in   a   fresh   specimen.      It   will   require 
less  time   and   patience   if   a   specimen  which   has   been 
hardened  in  alcohol  or  by  boiling  be  used.     It  may  best 
be  studied  in  a  specimen  which  has  been  soaked  for  a  few 
days  in  10-per-cent  nitric  acid. 

Remove  the  mussel  entirely  from  its  shell,  and  pin  it 
in  a  dissecting  pan,  with  its  dorsal  surface  down.  Sepa- 

1  It  may  be  demonstrated  by  injecting  the  alimentary  canal  through 
the  mouth  with  starch  mass  (see  Appendix,  p.  284)  colored  with  lamp- 
black, and  dissecting  away  the  sheet  of  overlying  muscle  of  one  side. 


148  MOLLUSKS. 

rate  the  two  pairs  of  gills  on  the  median  ventral  line,  and 
find  directly  beneath  the  posterior  adductor  muscle  a  pair 
of  yellowish  ganglia  more  or  less  united.  These  are  the 
visceral  ganglia.  Trace  from  them  as  a  center  a  pair  of 
lateral  nerves  to  the  gills,  a  pair  of  posterior  nerves 
to  the  edges  of  the  two  mantle  lobes,  and  a  pair  of  very 
long  commissural  nerves  forward,  to  join  a  pair  of  cere- 
bral ganglia  which  lie  near  the  surface  at  the  bases  of 
the  labial  palps,  on  either  side  of  the  mouth.  From  these 
ganglia  trace  a  pair  of  nerves  downward  to  the  pedal 
ganglia,  which  lie  deeply  imbedded  where  the  foot  joins 
the  abdomen.  The  nerves  appear  as  fine  white  threads  ; 
the  ganglia  are  usually  more  easily  seen  because  of  their 
yellowish  color.  These  three  pairs  of  ganglia,  with  their 
connecting  commissures,  constitute  the  central  nervous 
system  of  the  mussel,  and  of  a  large  group  of  animals  of 
which  it  is  a  type. 

IV.  Reproductive  Organs  lie  in  the  posterior  part  of  the 
abdomen,  one  on  each  side,  and  each  opens  by  a  slit  on  the 
upper  surface  just  above  the  long  commissural  nerve  traced 
forward  to  the  cerebral  ganglia. 

The  eggs  of  the  river  mussel  are  passed  into  the  cavity 
of  the  outer  gill,  where  they  hatch,  and  where  the  young 
are  retained  for  a  time.  If  there  be  found  a  specimen  in 
which  the  outer  gills  appear  swollen  and  dark  colored, 
open  one  of  them,  and  mix  a  little  of  the  contents  with  a 
drop  of  water  on  a  slide.  Examine  with  low  power,  and 
look  for  little  mussels.  Draw  several  of  them.  Notice 
whether  any  of  them  move  about. 

V.  The  Shell.  —  Remove  all  muscles  from  the  inside, 
and  dirt  from  the  outside,  of  the  shell,  and  observe  again 
the  concentric  lines  of  growth  about  the  umbones.     Hold 
the  shell  up  toward  the  light,  and  observe  the  fine  lines 
radiating  from  the  umbones. 

Inside  the  shell,  notice  the  large  adductor  muscle  scars, 


THE   RIVER   MUSSEL.  149 

and  close  beside  them  the  smaller  but  often  deeper  scars 
of  the  retractor  muscles.  Observe  a  narrow  linear  muscle 
impression,  —  a  curved  line  marked  around  the  free  border 
of  the  valve,  about  half  an  inch  from  the  edge.  This  is 
the  line  along  which  the  mantle  was  found  clinging.  It 
is  therefore  called  the  pallial  line. 

Observe  the  hinge  teeth  between  the  dorsal  edges  of  the 
two  valves.  Open  and  close  the  valves,  and  see  how  these 
interlock.  They  hold  the  valves  together  very  firmly, 
when  closed.  The  blunt,  irregular,  serrated  ones  between 
the  umbones  are  the  cardinal  teeth.  The  long,  narrow, 
shelf -like  folds  of  pearl  beneath  the  hinge  are  the  lateral 
teeth. 

Observe  that  the  shell  consists  of  three  layers :  — 

1.  An  outer  layer  of  horny,  brownish,  or  greenish  epi- 
dermis, which  was  continuous  at  the  edges  of  the  shell 
with  the  border  of  the  mantle.     The  hinge  at  the  back  is 
a  modified  and  very  elastic  portion  of  the  epidermis. 

2.  An  inner,  pearly  layer.     This  is  seen,  under  magnifi- 
cation, to  consist  of  thin,  flat  layers  of  pearl,  the  edges  of 
which  appear  as  fine,  sinuous  lines.     These  cause  inter- 
ference in  the  light  waves  that  fall  upon  them,  and  give 
rise  to  all  the  singularly  beautiful  colors  seen  within  the 
fresh  shells  of  some  Unios. 

3.  A  darker  middle  layer,  seen,  under  magnification,  to 
consist  of  polygonal  prisms  placed  perpendicular  to  the 
surface  of  the  shell. 

Dissolve  out  the  mineral  matter  from  a  shell  by  placing 
it  for  a  time  in  dilute  acid.  What  properties  has  the 
remaining  part  ? 

Burn  out  the  animal  matter  from  a  number  of  shells. 
Weigh  them  before  throwing  them  into  the  fire  and  after 
taking  them  out,  and  note  the  proportional  loss.  Pick  a 
burned  shell  to  pieces,  and  note  the  disposition  of  layers 
in  its  thickened  part. 


150  MOLLUSKS. 

The  Life  Process.  —  Since,  in  connection  with  each  of 
the  organs  studied,  the  work  it  has  to  do  has  been  already 
mentioned,  it  only  remains  to  summarize  these  various 
operations  as  parts  of  the  process  by  which  the  life  of  the 
animal  is  maintained. 

I.  Nutrition.  —  This  part  of  the  process  is  dependent 
to  a  marked  extent  upon  the  aquiferous  system,  and  the 
water  currents  it  keeps  up.  The  siphons  are  the  most 
conspicuous  part  of  this  system ;  but  the  cilia  lining  the 
openings  into  the  gills,  although  the  least  conspicuous, 
are  the  most  important  part  of  it,  for  it  is  by  their  lash- 
ing action  that  the  water  is  drawn  into  one  siphon  and 
driven  into  and  through  the  gills  and  out  through  the 
other  siphon.  In  the  gills  the  usual  exchange  of  car- 
bonic-acid gas  for  oxygen  takes  place  between  the 
water  flowing  freely  over  the  thin-walled  blood  vessels 
distributed  throughout  the  gills  and  the  blood  flowing 
inside  those  vessels.  In  other  animals  that  breathe  by 
gills  this  exchange  seems  to  be  the  sole  purpose  of  the 
water  currents,  but  in  the  mussel  these  currents  also  assist 
in  the  procuring  of  food  and  in  excretion.  The  food  con- 
sists chiefly  of  low  plant  organisms  found  free  in  the  water. 
These  are  carried  into  the  branchial  chamber  by  the  enter- 
ing current.  The  current  does  not  all  enter  the  gills,  but 
a  branch  of  it  is  driven  forward  toward  the  anterior  end 
of  the  body,  and  the  bits  of  food  carried  along  by  it  are 
directed  by  the  labial  palps  into  the  mouth.  Excreta  are 
expelled  with  the  current  passing  through  the  cloacal 
siphon.  Thus  all  the  operations  connected  with  nutrition 
are  more  or  less  directly  dependent  on  the  water  currents. 

For  convenience  in  summarizing,  we  may  say  that  ru- 
trition  is  effected  in  the  river  mussel  through  the  agency 
of  the  following  interdependent  systems  of  organs  :  — 

1.  A  digestive  system,  comprising  the  alimentary  canal 
and  the  large  accessory  gland  called  liver. 


THE    RIVER   MUSSEL.  151 

2.  A  circulatory  system,  comprising  (1)  veins  which  col- 
lect blood  from  all  the  tissues  and  convey  it  to  the  gills ; 
(2)  other  (branchial)  veins,  which   convey   the   aerated 
blood   from  the  gills  to  the  heart ;    (3)  auricles,  which 
receive  the  blood  from  the  gills,  and,  contracting,  pass  it 
on  into  (4)  the  ventricle,  which  in   turn  contracts,  and 
drives   it  through  (5)  the  arteries,  out  into  the  tissues 
again. 

Four  important  changes  take  place  in  the  blood  during 
its  course  through  the  body  :  — 

(a)  It  is  enriched  by  the  digested  food,  which  it 
receives  directly  through  the  walls  of  the  alimentary 
canal. 

(6)  In  the  tissues  the  cells  with  which  it  comes  in  con- 
tact take  from  it  whatever  material  they  need  for  growth, 
and  return  to  it  their  waste  products  of  oxidation. 

(<?)  On  its  return  to  the  gills,  part  of  the  blood  passes 
through  the  renal  organ,  where  nitrogenous  waste  products 
are  taken  from  it  for  excretion. 

(d)  In  its  passage  through  the  gills  it  loses  waste  car- 
bonic acid,  and  absorbs  oxygen. 

3.  A   respiratory   system,    comprising   the   gills,   with 
their  numerous  small  blood  vessels. 

4.  An  aquiferous  system,  comprising   the   siphons  and 
the  ciliated  passageways  through  the  gills. 

5.  An  excretory  system,  of  which  the  renal  organs  and 
the  gills  comprise  the  most  important  part. 

Metabolism  is  in  this,  as  in  all  other  animals,  performed 
by  the  individual  cells. 

Certain  of  the  mantle  cells  take  calcium  carbonate  from 
the  blood,  and  deposit  it  as  a  precipitate,  thus  forming  the 
mineral  part  of  the  shell.  The  soft  inner  part  of  the 
mantle  thus  continues  through  life  to  deposit  on  the  inside 
of  the  shell  a  layer  of  pearl.  If  a  foreign  body  get  into 
the  substance  of  the  mantle,  or  get  between  the  mantle 


152  MCXLLUSKS. 

and  the  shell,  it  will  be  covered  with  a  layer  of  pearl. 
This  is  the  way  that  the  pearls  of  commerce  are  produced ; 
and  inferior  pearls  are  often  found  in  dissecting  our  com- 
mon river  mussels. 

II.  Reproduction.  —  The   eggs,  as  already  noticed,  are 
fertilized,  hatched,  and  the  young  are  nurtured  for  a  time 
in  the  outer  gills  of  the  female.     Their  number  is  pro- 
digiously great.     The   young,  when   found   in   the   gills 
(then  called  glochidicC),  differ  very  markedly  in  appearance 
from  the  adults,  in  their  widely  gaping,  triangular  valves, 
hooked  at  the  tip.     When  they  are  expelled  from  the  gills 
into  the  water,  to  shift  for  themselves,  they  fasten  them- 
selves by  means  of  these  hooks  to  some  floating  or  swim- 
ming object,  preferably  to  the  fins  of  a  fish  or  to  the  tail 
of  a  tadpole,  where  they  lead  for  a  time  apparently  a  para- 
sitic existence.     Later  they  fall  to  the  bottom,  and  begin 
life  independently.     Doubtless  multitudes  of   those  that 
fall  to  the  bottom  are  buried  in  the  shifting  mud  and 
sand ;  many  more  are  eaten  by  other  aquatic  animals  be- 
fore their  shells  have  attained  sufficient  size  and  strength 
to  afford  them  protection ;  and  even  in  adult  life  some  are 
eaten  by  minks  and  otters,  and  very  many  are  left  out  on 
the  banks  by  receding  floods  to  die  of   evaporation :    so 
that  the  vast  number  of   eggs  produced  appears,  in  the 
end,  after  taking  all  casualties  into  account,  to  be  only 
sufficient  to  maintain  for  the  species  its  accustomed  num- 
bers, and  to  keep  up  the  biological  balance  in  the  life  of 
the  river  beds. 

III.  Voluntary  Motion.  —  The  muscular  system  serves 
the  river  mussel  the  double  purpose  of  performing  its 
movements,  and  of  holding  it  in  its  shell.     The  strongest 
muscles  are  the  adductors,  which  close  the  shell.    Opposed 
to  these  is  only   the  hinge   ligament,  which,  upon  their 
relaxation,  opens  the  shell  automatically. 

The  foot  is  principally  a  muscular  organ  consisting  of 


THE   KIVER   MUSSEL.  153 

longitudinal  fibers  of  the  oblique  pedal  muscles,  capable 
of  retracting  it,  or  of  moving  it  sidewise,  and  of  circular 
fibers  capable  of  extending  it.  It  is  adapted  for  plowing 
through  mud  or  sand,  and  for  no  other  kind  of  locomotion. 
Only  by  sinking  the  foot  into  mud  or  sand  is  the  animal 
able  to  rise  to  its  erect  position.  Blood  is  forced  down 
the  pedal  artery  through  the  center  of  the  foot  into  its 
point,  as  an  additional  aid  to  its  extension;  and  by  the 
distension  of  its  tip  a  firmer  hold  is  obtained  in  the  sand, 
to  aid  in  locomotion.  The  flat  muscle  of  the  mantle  is 
capable  of  moving  its  entire  margin. 

IV.  Sensation.  —  The  nervous  system  of  the  mussel 
consists  of  the  three  pairs  of  ganglia  already  noticed,  and 
of  nerves  radiating  from  each  pair  extending  to  every 
vascular  part  of  the  body,  giving  sensibility  to.  every  part, 
and  furnishing  nervous  communication  with  every  other 
part. 

The  senses  are  not  very  acute.  Touch  is  well  devel- 
oped, and  is  most  acute  in  the  point  of  the  foot  and  in  the 
mantle  margin,  particularly  in  the  part  which  forms  the 
outer  border  of  the  siphons.  Taste  and  smell  are  prob- 
ably developed  slightly,  and  aid  the  animal  somewhat  in 
the  selection  of  food.  Sight  and  hearing  are  developed 
but  feebly,  if  at  all.  There  is  a  so-called  ear  sac  in 
the  foot,  near  the  pedal  ganglia.  That  it  is  an  organ  of 
hearing  is  very  doubtful.  It  seems  more  probable  that  it 
is  an  organ  of  the  sense  of  equilibrium,  enabling  the  ani- 
mal to  distinguish  between  a  flat  or  inclined  position  and 
an  erect  position.  Though  incapable  of  hearing  sound, 
the  animal  may  feel  vibrations  when  they  become  suf- 
ficiently intense.  The  siphon  fringes  are  so  sensitive  to 
light,  that  a  heavy  shadow  thrown  across  them  will  cause 
them  to  be  retracted. 

The  instincts  of  this  animal  are  of  a  low  order :  they 
seem  to  be  limited  to  self-preservation  and  the  selection 


154  MOLLUSKS. 

of  food.  A  complete  retreat  within  its  shell  is  its  only 
means  of  defense.  But  the  hard,  closed  shell  is  protec- 
tion, strong  in  proportion  as  the  instincts  are  weak. 

The  river  mussel  is  a  representative  of  the  group  Mol- 
lusca  (or  soft-bodied  animals). 

Other  Mollusks.  —  There  are  three  forms  of  snails, 
very  common  throughout  the  interior :  (1)  land  snails, 
found  under  the  fallen  leaves  and  decaying  logs  in  hard- 
wood groves,  and  easily  collectible  in  warm  weather ; 
(2)  pond  snails,  found  on  the  submerged  vegetation  of 
ponds  throughout  the  year;  (3)  river  snails  (opercu- 
lates),  found  in  the  same  situations  with  river  mussels. 
The  most  available  of  these  for  study  in  the  winter  is  the 
pond  snail. 

THE  POND  SNAIL. 

(Limnea.) 

Haunts.  —  This  animal  may  be  found  in  almost  every 
natural  small  pond,  adhering  closely  to  the  stems  and 
leaves  of  aquatic  plants,  to  the  dead  stems  of  "  cat-tail 
flags,"  to  sticks,  boards,  old  boots,  etc.  ;  in  fact,  to  almost 
anything  that  may  have  chanced  to  get  into  the  water. 
These  things  may  be  slowly  drawn  out  of  the  water,  and 
the  snails  picked  off  them  by  hand. .  The  only  apparatus 
necessary  for  collecting  pond  snails  is  a  small  vessel  of 
water  to  carry  them  home  in. 

Aquarium  Study.  —  They  may  be  kept  in  an  aquarium, 
or,  better  for  study,  in  a  bowl,  or  dish,  or  fruit  jar,  in 
water.  The  vessel  should  be  kept  clean,  and  they  should 
be  fed  daily  with  leaves  of  cabbage  or  lettuce.  They 
are  very  easy  to  keep ;  there  is  much  that  is  novel 
and  interesting  in  their  habits  that  is  quite  easy  of 


THE  POND   SNAIL. 


155 


observation ;  and   every  student  should   keep  a  number 
of  them  awhile  for  his  own  study. 

In  a  fully  extended  specimen,  observe,  first,  the  three 
distinctive  and  obvious  characters  of  mollusks:  (1)  the 
foot  beneath  the  body,  (2)  the  mantle  covering  its  back, 
and  (3)  the  shell  secreted  by  the  mantle.  The  foot  is  the 
broad,  flat  disk  on  which  the  ani- 
mal creeps  ;  the  mantle  edge  is  just 
visible  within  the  edge  of  the  shell. 


The  Shell.  —  Study  the  shell. 
Observe  that  it  is  in  one  piece 
(univalve),  whereas  the  shell  of  the 
mussel  is  in  two  pieces  (bivalve). 
Its  parts  are  named  as  follows :  — 

1.  The  apex  is  the  pointed  end. 

2.  The  aperture  is  the  opening 
at  the  large  end. 

3.  The  lip  is  the  outer  edge  of 
the  aperture. 

4.  The  lines  of  growth  are  par- 
allel to  the  lip. 

5.  The  suture  is  the  spiral  groove 
on  the  outside. 


DIAGRAM  OF  POND  SNAIL  : 
a,  apex;  s,  suture;  sp, 
spire;  I,  lip;  1,  2,  3,  4, 
whorls  of  shell,  the  larger 
ones  showing  lines  of 
growth  (the  aperture  is 
filled  with  the  body  of 
the  animal) ;  c,  collar 
(edge  of  mantle)  pro- 
truding beneath  the  lip; 
h,  head;/,  foot;  e,  eye; 
t,  tentacle ;  6,  breathing 
aperture. 


6.  The  spire  comprises  all  the  whorls  or  turns  of  the 
shell  taken  together. 

7.  The  columella  is  the  axis  of  the  spire. 

If,  when  holding  the  shell  with  the  apex  toward  you, 
the  whorls,  as  they  proceed  from  you,  turn  to  the  right, 
above  the  axis  of  the  spire,  the  spire  is  right  hand,  or 
dextral ;  if  they  turn  the  other  way,  it  is  left  hand, 
or  sinistral. 

In  the  river  snails  an  operculum  will  be  found,  —  a  lid- 
like  piece  which  completely  closes  the  aperture  when 
the  animal  is  retracted  within  the  shell. 


156  MOLLUSKS. 

External  Features.  —  Study  the  external  features  of  the 
snail  by  careful  inspection  of  live  and  active  specimens 
moving  about  in  a  glass  vessel.  Observe  that  the  foot 
is  bilaterally  symmetrical,  that  it  tapers  to  an  obtuse 
point  behind,  that  it  is  squarish  or  truncated  in  front, 
and  that  its  foremost  part  is  marked  off  from  the  rest  by 
a  transverse  groove  on  the  ventral  side.  Observe,  on  the 
dorsal  side  of  this  part,  a  pair  of  long  motile  and  retrac- 
tile tentacles,  'and  a  pair  of  eyes  appearing  as  dark  spots  at 
their  bases.  On  the  ventral  side  of  this  part  is  the  mouth, 
easily  seen  in  a  specimen  that  is  crawling  on  the  side  of 
the  glass  vessel. 

Observe  the  long,  flexible  body,  extending  upward  from 
the  foot  into  the  spire. 

Observe  that  the  mantle  is  thickened  at  its  edge  where 
it  lines  the  edge  of  the  aperture.  This  part  is  the  collar. 

Observe  in  snails,  at  the  surface  of  the  water,  a  conspicu- 
ous orifice  in  the  collar  at  the  right  side  of  the  body. 
This  is  the  respiratory  orifice.  The  mantle  is  pushed  in 
at  this  point,  and  distended  within  into  a  sort  of  bag- 
like  rudimentary  lung,  in  the  walls  of  which  the  minute 
blood  vessels  are  distributed. 

Habits.  —  Study  the  actions  of  the  snail.  How  is  its 
peculiar  crawling,  creeping,  or  gliding  locomotion  effected  ? 
Note  that  it  moves  with  equal  ease  on  the  bottom,  on  the 
sides,  and  in  inverted  position  along  the  surface  of  the 
water.  It  will  be  seen  to  come  to  the  surface  at  more  or 
less  regular  intervals  for  a  fresh  supply  of  air,  and  may 
sometimes  be  seen  expelling  a  bubble  of  impure  air  before 
taking  in  a  fresh  supply.  It  will  be  seen  to  close  its  respir- 
atory orifice  before  going  down  again.  Occasionally  a 
snail  may  be  seen  to  let  itself  down  from  the  surface 
by  a  floating  thread  of  mucus  secreted  by  glands  in  the 
foot.  When  a  number  of  snails  going  in  opposite  direc- 


THE   POND   SNAIL.  157 

tions  meet,  one  may  sometimes  be  seen  using  its  shell  as  a 
means  of  offense,  clearing  its  track  by  striking  about  with 
its  spire.  If  the  mouth  of  one  that  is  crawling  on  the 
side  of  glass  be  watched  with  a  lens,  its  ribbon-shaped 
radula,  covered  with  rows  of  minute,  recurved  teeth,  may 
sometimes  be  seen  slightly  protruded.  By  means  of 
muscles  attached  at  both  ends,  the  radula  is  drawn  back- 
ward and  forward  like  a  rasp  across  the  objects  on  which 
the  snail  feeds.  Cabbage  leaves  on  which  the  snail  has 
been  fed  will  show  areas  which  have  been  "  scraped  "  by  the 
radula.  All  these  things  and  many  more  may  be  seen  by 
carefully  watching  a  few  live  snails  in  a  tumbler  of  water. 

Development.  —  The  eggs  of  the  pond  snail  are  very 
easily  procured,  and  they  offer  exceptionally  fine  advan- 
tages for  the  study  of  those  stages  of  development  which 
immediately  succeed  fertilization.  They  are  laid  in  gelat- 
inous, transparent  capsules,  half  an  inch  to-  an  inch  in 
length,  flattened,  and  linear  or  oblong  in  outline.  After 
a  few  snails  have  been  kept  a  short  time  in  a  small  vessel 
of  water  with  their  appropriate  food,  these  egg  capsules 
may  be  looked  for  on  the  bottom  and  sides  of  the  vessel, 
or  closely  adherent  to  the  stems  or  leaves  of  plants  placed 
in  the  water.  They  are  so  transparent  as  to  be  easily 
overlooked. 

Detach  one  of  these  egg  capsules  by  pushing  a  thin 
blade  between  it  and  its  support.  Place  it  in  a  watch  glass 
with  a  little  water,  for  examination. 

Examine  it  with  a  lens,  and  draw  it.  How  many  eggs 
does  it  contain?  How  are  these  eggs  arranged  in  the 
capsule?  What  is  the  shape  of  each  egg? 

Note  that  each  egg  contains  a  minute  oosperm  (or  fer- 
tilized ovum),  which  is  less  transparent  than  other  parts. 
It  is  the  development  of  this  oosperm  that  especially 
invites  our  study. 


158  MOLLUSKS. 

I.  Segmentation.  —  Place  the  watch  glass  upon  the  stage 
of  the  microscope,  and  examine  the  eggs  with  IOAV  power. 
If  a  freshly  laid  capsule  has  been  obtained,  the  oosperm 
of  each  egg  \vill  appear  perfectly  spherical  in  form,  and 
slightly  yellowish  in  color,  from  the  large  number  of 
minute  food-yolk  granules  distributed  through  it.  If  it 
be  kept  covered  with  water,  and  watched  at  intervals  of 
half  an  hour  or  less  during  the  first  day,  and  at  intervals 
of  half  a  day  thereafter  until  hatched,  the  following 
changes  may  be  confidently  expected :  — 

The  oosperm  is  practically  a  single  large  cell,  formed 
by  the  fusion  of  two  specialized  reproductive  cells  called 
ovum  and  sperm.  The  fusion  of  the  two  we  have 
already  called  fertilization,  and  have  said  that  it  is  essen- 
tially the  same  process  in  all  animals  except  the  pro- 
tozoans. Fertilization  necessarily  precedes  and  initiates 
the  changes  which  we  are  now  to  study. 

The  oospeima  divides,  and  becomes  two  spherical  cells 
instead  of  one  ;  after  a  short  quiescent  period,  the  two 
divide,  and  become  four ;  after  another  short  period,  the 
four  divide,  and  become  eight ;  and  so  on,  with  decreasing 
regularity.  This  process  is  called  segmentation. 

If  all  the  eggs  in  a  freshly  laid  capsule  be  examined, 
some  of  the  oosperms  will  be  sure  to  show  a  lighter  and 
a  darker  side.  This  is  owing  to  a  greater  accumulation 
of  yolk  granules  at  one  side  of  the  sphere.  Some  will 
show,  also,  one  or  two  minute  transparent  polar  bodies 
pushed  out  from  the  middle  of  the  lighter  side.  That  pole 
of  the  sphere  at  which  they  appear  is  called  the  formative 
pole.  In  segmentation,  a  groove  first  appears  at  the  forma- 
tive pole,  extends  meridionally  around  the  oosperm,  and 
deepens  until  two  separate  cells  are  formed.  These  cells 
appear  to  partly  coalesce  again,  before  the  next  division. 
Then  a  second  groove  starts  at  the  formative  pole,  and  ex- 
tends meridionally  around  the  two  cells  at  right  angles  to 


THE   POND   SNAIL.  159 

the  first  groove,  and  deepens  until  the  two  cells  are  divided 
into  four.  Then  an  equatorial  groove  at  right  angles  to 
both  first  and  second  grooves  divides  the  four  cells  into 
eight.  This  last  division  is  an  unequal  one,  however ; 
for  the  groove  is  not  at  the  equator  of  the  sphere,  but 
nearer  the  formative  pole.  It  therefore  pinches  off  four 
small  cells  at  the  formative  pole,  and  leaves  four  large 
ones,  composing  the  greater  part  of  the  sphere. 

It  must  be  observed  here  that  these  grooves  are  but  the 
external  evidence  of  processes  going  on  inside.  They  are 
the  result,  and  not  the  cause,  of  the  division.  The  cell 
material  separates  into  two  portions  ;  and  the  two  portions, 
moving  apart,  leave  grooves  between. 

After  the  eight-cell  stage  has  been  reached,  the  cells 
divide  with  less  regularity.  The  small,  active  cells,  of 
nearly  clear  protoplasm,  at  the  formative  pole,  divide 
very  rapidly  ;  the  large,  yolk-encumbered  cells  divide  very 
slowly,  so  that  the  later  stages  in  segmentation  are  ob- 
scured, and  sixteen-cell,  thirty-two-cell,  sixty-four-cell, 
etc.,  stages  are  not  discoverable.  But  the  one-cell,  two- 
cell,  four-cell,  and  eight-cell  stages  are  very  plain,  and 
easily  followed ;  and  these  illustrate  the  process  of  seg- 
mentation. 

II.  Later  Stages.  —  Two  later  stages,  which  are  com- 
mon to  most  of  the  higher  animals,  may  be  observed  in 
the  development  of  the  snail.  These  are  :  — 

1.  The  Uastula  stage,  in  which  the  segmentation  pro- 
cess results.      In  this  stage  there  is  a  hollow  sphere  of 
cells,  its  walls  a  single  layer.     The  Uastula  is  not  quite 
spherical,   and   its  walls  are  not   of   uniform   thickness, 
being  formed  of   a  few  large    cells  on  one  side,  and  of 
more  numerous  small  ones  on  the  other. 

2.  The  gastrula  stage,  in  which  one  side  of  the  hollow 
sphere  has  become  pushed  in,  as  it  were ;  the  other  side 
extending   its  edges,  forming   a   cup-shaped  depression. 


160  MOLLtTSKS. 

This  depression  deepens,  its  aperture  narrows,  and  a  more 
or  less  spherical  form  is  again  assumed.  It  is  obvious 
now  that  the  sphere  has  double  walls,  and  that  its  cavity 
has  an  open  communication  with  the  exterior.  It  is  now 
called  a  gastrula. 

Compare  the  gastrula,  as  to  the  type  of  its  structure, 
with  a  hydra  stripped  of  its  tentacles. 

The  later  stages  within  the  egg  are  not  such  as  are 
common  to  most  of  the  higher  animals.  They  are  difficult 
of  study,  and  they  will  not  be  described  here  in  detail. 
The  student  will  readily  see  that  the  gastrula  grows, 
transforms  into  a  creature  less  simple,  and  begins  to  turn 
round  and  round  in  the  albumen  of  its  egg  by  means  of 
a  circlet  of  cilia  which  it  has  acquired.  As  it  increases 
in  size,  dorsal  and  ventral  surfaces  become  distinguish- 
able, a  transparent  matrix  of  a  shell  appears,  and  a  foot, 
with  a  head  imperfectly  marked  off  at  its  anterior  end. 
A  pair  of  blunt  processes  at  the  sides  of  the  head  fore- 
shadow tentacles,  and  two  very  black  pigment  spots  repre- 
sent the  eyes.  A  pulsating  heart  becomes  visible  through 
the  shell,  and  near  it  a  tubular  esophagus ;  and  by  the 
time  it  has  eaten  all  the  egg  contents,  and  is  ready  to 
come  forth,  most  of  the  adult  structures  are  recognizable. 

It  will,  no  doubt,  be  more  convenient  to  find  all  these 
stages  in  eggs  taken  from  different  capsules  than  to  try  to 
follow  the  transformations  through  with  a  single  capsule. 
If  a  goodly  number  of  capsules  are  obtainable,  it  is  quite 
possible  to  find  all  these  stages  at  one  time. 

The  young  snail  within  the  egg  is  called  an  embryo, 
and  all  the  transformations  by  which  it  comes,  from  being 
a  simple,  undifferentiated  cell,  to  the  possession  of  perma- 
nent and  serviceable  organs,  constitute  its  embryology.* 

1  Try  on' s  Structural  and  Systematic  Conchology  is  recommended  for 
reference,  and  for  use  in  making  a  further  study  of  mollusks. 


VERTEBRATES. 

THE   CATFISH. 

The  following  directions  are  written  with  special  refer- 
ence to  the  common  channel  cat  or  white  catfish  (Ictalu- 
rus  punctatus),  but  they  are  general  enough  to  be  applied 
without  difficulty  to  the  study  of  any  other  common  cat- 
fish. 


THE  CHANNEL  CAT  (after  Todd,  by  permission). 

Description.  —  The  channel  cat  is  abundant  in  all  oui 
rivers  and  small  streams.  It  has  the  characteristic  cat- 
fish contour  of  body,  which  needs  to  be  seen  but  once 
to  be  remembered.  It  is  olivaceous  above,  and  whitish 
below,  with  silvery  sides ;  and  its  tough,  scaleless  skin  is 
sprinkled  with  many  small,  round,  dark  olive  spots.  It 
may  be  angled  for  at  the  proper  season,  and  may  be 
obtained  in  the  market  or  from  fishermen  at  all  seasons, 
for  it  is  a  good  food  fish. 

Like  all  the  other  catfishes,  it  is  very  tenacious  of  life, 
and  there  is  little  trouble  in  obtaining  live  specimens  from 

NEED.  ZOOL. 11  161 


162  VERTEBRATES. 

a  distance,  when  this  is  necessary.  Specimens  are  often 
seen  alive  in  the  markets,  in  cool  weather,  twenty-four 
hours  or  more  after  they  have  been  taken  from  the  water. 

Aquarium  Study.  —  Study  a  live  specimen  that  has 
been  placed  in  an  aquarium,  or  tank,  or  tub  of  water. 
Observe  its  form,  its  coloration,  its  markings,  its  method 
of  getting  about.  What  adaptations  can  you  discover  in 
its  form  to  locomotion  in  water  ?  To  living  on  the  muddy 
bottoms  in  river  channels  ? 

Observe  the  large  eyes,  the  mouth'  opening  directly  for- 
ward, the  long  barbels  at  the  corners  of  the  mouth,  a 
pair  of  smaller  barbels  above  and  behind  the  mouth,  and 
two  pairs  below  and  behind  the  mouth. 

Observe  on  either  side  of  the  head,  where  it  joins  the 
body,  a  wide  strip  of  membrane  overlapping  a  long  ver- 
tical slit.  Notice  the  regular  opening  and  closing  of  this 
aperture,  and  also  of  the  mouth,  and  note  the  concerted 
action  between  the  two.  Place  a  drop  of  ink  in  the  water, 
close  in  front  of  the  mouth,  to  discover  the  direction  of 
the  current  of  water  through  these  openings. 

I.  Fins.  —  Four  of  these  are  paired  fins,  —  the  pair  at 
the  sides  of  the  body,  just  back  of  the  head,  are  the 
pectoral  fins  ;  the  pair  low  down  on  the  sides  of  the  body, 
much  farther  back,-  are  the  ventral  fins,  —  the  others  are 
single  or  unpaired  fins.  The  two  fins  on  the  median  dorsal 
line  are  dorsal  fins.  The  one  on  the  median  ventral  line  is 
the  anal  fin.  The  large  one  at  the  posterior  end  of  the 
body  is  the  caudal  fin. 

As  the  fish  swims  about,  watch  it  to  discover  the  use  of 
each  of  these  fins.  That  the  large  caudal  fin  is  the  one 
principally  concerned  in  locomotion  will  be  seen  at  once. 
To  learn  the  use  of  the  pectoral  and  ventral  fins,  catch  the 
fish  with  the  hand,  avoiding  the  sharp  spines  at  the  front 
of  pectoral  and  anterior  dorsal  fins ;  fold  the  pectoral  fins 


THE   CATFISH.  163 

backwards,  flat  against  the  sides  of  the  body;  pass  a  rubber 
band  back  over  the  head  and  around  these  fins,  to  keep 
them  so.  Keep  the  fish  under  water  while  attempting 
to  depress  the  pectoral  spines,  for  in  air  it  will  keep 
them  rigidly  erect.  Pass  another  rubber  band  about  the 
ventral  fins.  Then  liberate  the  fish,  and  watch  it.  What 
position  does  its  body  assume  ? 

Release  the  paired  fins,  and  fasten  down  the  dorsal  and 
anal  fins  with  rubber  bands.  Liberate  the  fish  again,  and 
observe  how  it  gets  along  without  the  use  of  these  fins. 
What  kind  of  a  course  does  it  take  through  the  water  ? 

II.  Circulation  seen  in  Fins.  —  Observe  that  the  broadly 
expanded  part  of  the  fin  is  very  thin  and  transparent,  and 
that  it  is  traversed  by  minute  blood  vessels,  which  appear 
as  fine  red  streaks.     Connecting  these  that  are  visible  to 
the  unaided  eye,  are  many  smaller    capillary  vessels  in 
which  the  circulation  can  be  advantageously  studied  with 
a  microscope,  as  follows  :  — 

Wrap  the  fish  in  a  wet  towel,  leaving  the  caudal  fin 
exposed,  and  place  it  on  a  low  box  beside  the  microscope, 
with  its  caudal  fin  extending  across  the  center  of  the  micro- 
scope stage.  Spread  the  fin  out  flat  on  a  glass  slip  upon 
the  stage,  so  as  to  bring  a  thin  portion  of  it  into  the  field, 
and  examine  it  with  low  power.  If  the  fish  refuses  to  lie 
quietly,  pour  a  little  chloroform  on  the  towel  near  its 
mouth. 

Observe  the  conspicuous,  dark,  irregular  pigment  cells 
scattered  throughout  the  epidermis  of  the  fin. 

III.  Blood  Vessels.  — The  larger  ones  are  of  two  kinds  : 
(1)  arteries,  bringing  blood  out  into  the  fin,  and  (2)  veins, 
conveying  the  blood  back  to  the  body  again.     The  smaller 
ones  are  the  capillaries,  connecting  the  arteries  with  the 
veins,  aiid  distributing  the  blood  throughout  the  tissues  of 
the  fin. 

Observe  that  the  blood  consists  of   a  fluid  plasma,  in 


164  VERTEBRATES. 

which  float  numerous  corpuscles.  Observe  that  the  blood 
appears  red  in  the  arteries  and  veins,  where  the  corpus- 
cles are  accumulated,  but  only  slightly  reddish  or  yellow- 
ish in  the  capillaries,  where  corpuscles  form  but  a  thin 
layer. 

Does  the  blood  travel  faster  in  the  arteries  and  veins,  or 
in  the  capillaries  ? 

Place  a  bit  of  cover  glass  over  a  very  thin  portion  of  the 
fin,  and  study  it  with  higher  power.  Find  two  kinds  of 
corpuscles  in  the  blood  :  (1)  red  corpuscles  (red  only  when 
a  number  are  seen  together),  very  numerous,  and  carried 
along  in  the  center  of  the  larger  currents  closely  packed 
together ;  and  (2)  white  corpuscles,  resembling  the  amoeboid 
corpuscles  of  the  mussel  and  earthworm,  not  very  numer- 
ous, and  usually  seen  trailing  along  the  edges  of  the  blood 
currents,  or  escaping  out  into  the  tissues. 

External  Features.  —  Kill  the  fish  with  chloroform,  and 
make  a  closer  study  of  its  external  features. 

Observe  the  exact  correspondence  of  the  two  sides,  — 
perfect  bilateral  symmetry. 

Observe  the  broad  head,  dorsally  depressed,  the  absence 
of  neck,  and  the  long,  tapering  body. 

On  the  upper  surface  of  the  head,  just  behind  the  mouth, 
find  four  nostril  openings,  the  posterior  pair  close  behind 
the  barbels  of  this  surface.  Probe  these  openings  with  a 
bristle  to  see  whether  they  have  any  connection  with  each 
other  or  with  the  mouth. 

Examine  the  bases  of  the  large  barbels  at  the  corners 
of  the  mouth,  to  find  the  bones  which  extend  out  into 
them  from  the  head. 

Examine  the  eyes.  Are  there  any  eyelids  or  other 
means  by  which  they  may  be  closed  ?  Press  on  the  edges 
of  the  eyeball  to  discover  how  far  it  may  be  turned  to  look 
in  different  directions.  Press  with  a  finger  against  the 


THE   CATFISH.  165 

roof  of  the  mouth  inside,  and  observe  how  the  eyeball  is 
affected. 

I.  The  Mouth.  —  Stretch  the  mouth  wide  open,  and  look 
into  it.  Observe  a  band  of  numerous  sharp,  small  teeth 
extending  across  its  margin,  above  and  below.  Rub  a 
finger  across  these  teeth  to  discover  in  what  direction 
they  point.  What  advantage  to  the  animal  in  their  incli- 
nation ? 

The  bone  which  forms  the  border  of  the  lower  jaw  is 
called  the  mandible.  The  bone  of  the  upper  jaw  which 
bears  the  teeth  is  called  the  premaxillary.  In  other  fishes 
several-  bones  of  the  roof  of  the  mouth  bear  teeth.  One 
of  these  is  the  maxillary,  which  in  the  catfish  is  reduced 
to  the  pair  of  rudiments  already  found  supporting  the 
bases  of  the  lateral  barbels. 

The  tongue  is  a  slight  angular  elevation  on  the  floor  of 
the  mouth.  Its  boundaries  are  marked  out  by  correspond- 
ing grooves  on  the  lower  surface  of  the  head. 

The  posterior  funnel-shaped  part  of  the  capacious  cavity 
seen  on  looking  into  the  mouth  is  the  pharynx.  The  phar- 
ynx tapers  into  the  esophagus  "in  the  distance."  On 
the  floor  of  the  pharynx  are  two  large  prominences  cov- 
ered with  teeth.  Rub  a  finger  across  these  teeth  to  dis- 
cover their  direction. 

On  either  side  of  the  pharynx  are  the  gill  arches,  bear- 
ing the  gills  on  their  outer  convex  edges,  and  separated 
by  five  vertical  slits.  Pass  a  pencil  in  at  the  mouth,  and 
out  through  one  of  these  slits  to  the  exterior.  On  the 
outside  observe  that  the  pencil  has  lifted  a  semicircular 
flap,  which  is  divided  by  an  oblique  groove  into  two  por- 
tions. The  lower  marginal  portion  is  the  operculum,  and 
the  upper  anterior  portion  is  the  prce-operculum.  The 
latter  is  directly  behind  the  eye,  and  forms  the  cheek 
of  the  fish.  The  inner  surface  of  the  operculum  is  cov- 
ered by  a  soft  lining  membrane  called  the  branchiostegal 


166  VERTEBRATES. 

membrane,  which  is  supported  by  bony  rays  called  the 
branchiostegal  rays  (or  simply  branchiostegals) .  When 
the  operculum  is  lifted,  the  four  vertical  series  of  red 
gills  may  be  seen  inside.  They  may  be  studied  more 
advantageously  after  dissection. 

Observe  a  longitudinal  lateral  line  on  each  side  of  the 
body  of  the  fish. 

II.  Structure  of  the  Fins.  —  Study  the  structure  of  the 
fins.  Each  is  made  up  of  a  double  fold  of  membrane  sup- 
ported (except  in  the  posterior  dorsal  fin)  by  bony  rays. 
The  rays  are  wanting  in  the  posterior  dorsal  fin,  and 
usually  fat  is  deposited  between  the  folds  of  membrane, 
whence  it  is  called  an  adipose  fin.  The  first  ray  in  each 
of  the  pectorals  and  in  the  anterior  dorsal  fin  is  hard  and 
unjointed.  It  is  developed  as  a  stout,  sharp-pointed  spine, 
with  two  serrated  edges.  It  is  articulated  with  the  bones 
of  the  pectoral  arch  by  a  beautiful  joint,  which  secures  it 
great  rigidity  when  erected,  and  makes  it  a  formidable 
weapon  of  defense.  The  other  rays  are  soft  and  jointed. 
Examine  them  carefully  with  a  lens.  Observe  that  they 
are  branched  or  split  into  parallel,  jointed  strips  at  their 
outer  ends.  Make  an  enlarged  drawing  of  one  of  the 
pectoral  fins,  and  another  of  the  caudal  fin. 

The  two  pairs  of  paired  fins  are  homologous  with  the 
two  pairs  of  limbs  of  higher  animals.  The  pectoral  fins 
are  articulated  upon  a  bony  pectoral  arch  and  the  ventral 
fins  upon  a  smaller  and  more  rudimentary  pelvic  arch, 
which  in  the  catfish  is  unconnected  with  other  parts  of 
the  skeleton. 

Dissection.  —  Dissect  the  fish  under  water,  and  study 
its  internal  structure.  If  a  prepared  skeleton  be  at  hand 
for  reference  in  locating  bony  parts,  it  will  be  of  great 
assistance  in  the  following  work.  With  a  pair  of  stout 
bone  snips  or  shears,  or  with  a  hatchet,  cut  off  the  dorsal 


THE   CATFISH.  167 

spine,  so  that  the  fish  may  be  placed  on  its  back  in  the 
water.  With  forceps  pinch  up  a  transverse  fold  of  the 
tough  skin  of  the  ventral  surface  opposite  the  anterior 
dorsal  fin,  and  cut  through  the  fold  with  sharp  scissors. 
Continue  the  cut  backward  to  the  vent,  and  forward  to 
the  bones  of  the  pectoral  arch,  taking  care  not  to  injure 
or  displace  any  of  the  organs  which  lie  directly  beneath 
the  thin  body  wall.  Turn  back  the  flaps  and  expose 
these  organs.  Observe  a  silvery  membrane,  the  perito- 
neum, lining  the  body  cavity. 

Internal  Features. — The  large  red  organ  close  up  under 
the  pectoral  arch  is  the  liver.  Two  conic-pointed  lobes 
run  from  it  forward  and  downward ;  and  two  broad,  flat 
lobes  extend  backward.  Turn  these  latter  forward,  and 
observe  under  the  one  on  the  right  side  of  the  body  a 
capacious  yellow  gall  bladder. 

Under  the  other,  the  left  lobe,  the  esophagus  extends 
backward  to  the  stomach,  which  lies  entirely  posterior  to 
the  liver.  Pass  a  probe  into  the  stomach  from  the  mouth. 
The  intestine  arises  from  the  left  side  of  the  stomach,  and 
curves  forward  and  to  the  right  side,  and  posteriorly  around 
the  stomach,  and  makes  a  number  of  irregular  turns  in 
passing  through  the  posterior  part  of  the  body  cavity. 

Behind  the  stomach  it  is  partially  concealed  by  the 
reproductive  organs,  —  whitish  organs  in  the  male ;  large, 
yellowish  organs  in  the  female,  —  varying  much  in  size 
with  the  age  of  the  specimen  and  with  the  season. 

Observe  that  the  intestine  is  looped  up,  and  held  in 
place  by  a  transparent  membrane  (the  mesentery).  Lift 
this,  and  observe  the  blood  vessels  in  it.  Observe  the 
blood  vessels  and  the  nerve  branches  spread  out  over  the 
anterior  end  of  the  stomach.  Turn  the  stomach  over  to 
the  right  side,  and  observe  an  elongated,  narrow,  white 
organ,  the  pancreas,  lying  along  its  dorsal  side. 


168  VERTEBRATES. 

Observe  two  ducts  entering  the  intestine  together,  near 
its  origin,  appearing  to  come  directly  from  the  liver. 
One  of  these  comes  from  the  gall  bladder,  and  the  other 
from  the  pancreas.  The  former  may  be  recognized,  if  dis- 
tended with  bile  forced  into  it  by  squeezing  the  gall 
bladder.  The  other  should  be  traced  from  its  origin  by 
dissection. 

Posterior  to  the  pancreas  is  a  conspicuous  dark-red 
organ,  abundantly  supplied  with  blood  vessels,  —  the 
spleen. 

Remove  the  reproductive  organs.  Cut  through  the 
bones  of  the  pectoral  arch.  Open  wide  this  incision  by 
pressing  downward  on  both  pectoral  spines  at  once. 
Wash  out  any  blood  that  may  have  flowed  from  the 
last  incision.  Turn  backward  the  anterior  lobes  of  the 
liver,  and  observe  that  the  peritoneum  rises  at  this  point 
to  meet  the  pectoral  arch,  and  is  perforated  by  the  esoph- 
agus, and  by  the  blood  vessels  extending  forward  from 
the  liver.  Trace  the  blood  vessels  through  it  to  the 
heart.  In  the  heart  observe  three  principal  divisions: 
(1)  a  postero-lateral,  irregular,  thin-walled  part,  the 
auricle  ;  (2)  a  larger,  oval,  muscular,  strongly  contractile, 
central  part,  the  ventricle;  (3)  a  smaller,  oval,  anterior 
portion  of  lighter  color,  and  noncontractile,  the  arterial 
bulb.  This  is  continued  forward  into  the  branchial  artery, 
which  soon  divides,  sending  one  branch  (aortic  arch)  to 
each  gill. 

Cut  off  the  branchial  artery  at  its  origin,  and  remove 
the  heart.  Cut  off  the  esophagus  close  to  the  pharynx. 
Notice  how  muscular  its  walls  are.  Remove  the  digestive 
tract  entire,  beginning  with  the  esophagus,  and  proceed- 
ing posteriorly,  cutting  only  the  peritoneum  where  it 
meets  the  body  wall.  Observe  other  internal  organs 
lying  dorsal  to  the  peritoneum.  Central  among  these  is 
a  large,  white  bag  filled  with  air,  the  air  bladder  or  swim- 


THE   CATFISH.  169 

ming  bladder,  an  organ  by  means  of  which  the  specific 
gravity  of  the  fish  may  be  increased  or  diminished  at  will. 
Find  a  duct  connecting  it  with  the  esophagus.  In  a 
few  fishes  its  walls  contain  capillary  blood  vessels  in  which 
the  blood  is  aerated.  It  is  homologous  with  the  lungs  of 
higher  animals. 

In  front  of  the  air  bladder  is  a  dark,  reddish-brown 
organ  called  the  pronephros  (or  head  kidney).  Its  function 
is  not  well  understood. 

Cut  the  duct  of  the  air  bladder,  and  lift  out  the  diges- 
tive organs.  Three  parts  of  the  intestine  not  heretofore 
noticed  are  easily  distinguishable  :  (1)  A  wide  portion 
immediately  succeeding  the  stomach,  called,  the  duodenum. 
Into  this  part  the  ducts  from  the  liver  and  from  the  pan- 
creas enter.  (2)  A  narrow,  much  convoluted  portion,  not 
well  marked  off  from  the  preceding,  called  small  intestine. 
(3)  A  wider  terminal  portion,  well  marked  off  from  the 
latter  by  a  hoodlike  fold  in  the  walls  of  the  canal,  and 
called  large  intestine. 

Entirely  remove  the  peritoneum,  and  find  the  special 
excretory  organs,  the  kidneys,  lying  dorsal  to  its  posterior 
portion.  These  are  of  a  dark  purplish  or  brownish  color, 
and  are  more  or  less  united  into  one  mass.  They  send 
back  a  duct  to  communicate  with  a  small  white  urinary 
bladder  beneath  the  vent,  and  to  open  to  the  exterior  by 
a  separate  pore  a  little  farther  back. 

A  string  of  irregular,  fatty  bodies  is  often  found  ex- 
tended lengthwise  on  either  side  of  the  median  line,  near 
the  kidneys. 

The  Axis  of  the  Body.  —  Remove  all  these  organs,  and 
observe  the  bones,  now  partially  laid  bare  on  the  dorsal 
side  of  the  cavity  they  occupied.  A  chain  of  bones  con- 
stituting the  spinal  column  extends  along  the  median  line 
from  the  head  to  the  posterior  end  of  the  body.  The 


170  VERTEBRATES. 

separate  bones  of  the  spinal  column  are  the  vertebrce. 
The  slender,  curved  bones  extended  laterally,  a  pair 
from  each  vertebra,  are  the  ribs.  Between  the  ribs 
observe  the  white  spinal  nerves,  coming  out  from  the 
spinal  cord,  which  is  a  part  of  the  central  nervous  system 
located  in  a  hollow  that  extends  longitudinally  through 
the  center  of  the  spinal  column. 

Gills.  —  Study  the  gills.  Continue  the  ventral  incision 
forward  exactly  on  the  median  line  to  the  mouth.  The 
narrowed,  anterior  portion  of  the  chest  between  the  gill 
openings  is  the  isthmus.  Observe  the  branches  of  the 
branchial  artery  going  to  each  gill.  These  will  be  better 
seen  in  an  injected  specimen.1  Deepen  the  cut  until  it 
divides  the  upper  wall  of  the  pharynx,  the  floor  of  the 
mouth,  and  the  mandible.  Then  draw  the  edges  of  the 
cut  apart,  and  expose  the  white  gill  arches.  Observe 
the  vertical  series  of  teeth  on  the  concave  side  of  each 
arch.  These  are  the  gill  rakers.  Note  their  position,  and 
the  size  of  the  teeth  on  the  different  arches.  What  is 
their  probable  use  ? 

Raise  and  depress  the  floor  of  the  mouth  of  one  side, 
and  study  the  action  of  the  gill  arches  and  the  rakers. 
Observe  the  joints  in  the  arches. 

Cut  through  the  isthmus  of  one  side  between  the  first 
gill  and  the  branchiostegal  membrane,  and  expose  the  red 
gills  on  the  back  or  convex  side  ^  of  the  gill  arches.  Ob- 
serve that  they  are  in  a  double  row  on  the  back  of  each 
arch. 

Find  on  the  branchiostegal  membrane  an  elongated 
reddish  patch,  which  is  a  rudiment  of  an  anterior  gill. 
With  sharp  scissors  cut  out  of  a  gill  arch  a  thin  trans- 
verse section  bearing  one  or  two  pairs  of  gill  filaments, 
and  examine  the  section  under  lowest  power  of  a  micro- 

1  See  Appendix,  pp.  284,  285. 


THE   CATFISH.  171 

scope.  Observe  in  the  groove  on  the  gill-bearing  surface 
of  the  arch  the  two  blood  vessels,  branches  of  the  branchial 
artery  and  vein.  Observe  the  distribution  of  the  minute 
blood  vessels  in  the  gill  filaments.  Examine  the  fifth  gill 
arch.  How  does  it  differ  from  the  other  four  ? 

The  Dorsal  Surface. — Turn  the  fish  over.  The  bones 
of  the  head  constitute  the  skull.  Observe  that  the  thick, 
dark  skin  of  the  dorsal  surface  rests  directly  upon  the  top 
of  the  skull.  Find  a  narrow  backward  process  from  the 
skull  extending  to  the  dorsal  spine. 

Cranium  and  Cranial  Nerves.  —  Remove  the  skin  from 
the  right  side  of  the  body  and  head,  and  from  the  whole 
upper  posterior  portion  of  the  skull.  Then  cut  away  the 
top  of  the  skull  and  expose  the  brain.  Remove  the  bone, 
with  great  care  not  to  injure  the  soft,  nervous  tissues  be- 
neath it.  The  bony  cavity  in  which  the  brain  lies  is  the 
cranium.  When  the  top  of  the  cranium  is  cut  away,  it 
will  be  seen  that  the  white  brain  does  not  fill  the  cranial 
cavity,  and  that  it  is  surrounded  within  the  cavity  by  a 
transparent,  semifluid  substance. 

Study  the  brain  as  to  its  general  features. 

Observe  that  it  tapers  posteriorly  into  the  spinal  cord, 
which  has  been  already  noticed,  extending  through  the 
spinal  column. 

Observe  the  nerves  that  start  out  from  the  brain.  Aris- 
ing within  the  cranium,  these  are  called  cranial  nerves. 
Observe  that  the  cranial  nerves  are  paired.  Several  pairs 
of  them  may  be  easily  distinguished.  The  two  extending 
forward  from  the  brain  nearest  the  median  line  are  the 
olfactory  nerves,  or  nerves  of  smell.  Cut  away  its  bony 
covering,  and  trace  one  of  these  to  its  termination  in  an 
olfactory  bulb,  beneath  the  communicating  nostrils. 

The  Optic  Nerve  and  the  Eye. — Just  behind  the  olfac- 
tory nerves  is  a  larger  pair  of  optic  nerves  extending  direct 


172  VERTEBRATES. 

to  the  eyes.  Trace  the  course  of  one  of  these.  Examine 
the  location  and  attachments  of  the  eyeball.  The  bony 
socket  in  the  skull  in  which  it  rests  is  the  orbit.  Find 
six  delicate  whitish  bands  of  muscle  extending  outward 
from  the  orbit,  and  attached  to  the  sides  of  the  eyeball. 
Observe  that  four  of  these  are  straight,  and  two  are 
oblique,  in  their  attachment ;  and  that  all  are  in  pairs, 
opposed  in  their  action.  Determine  in  what  direction  the 
contraction  of  each  would  move  the  eyeball. 

A  small  cranial  nerve  (the  oculomotor)  is  distributed 
to  these  muscles. 

Cut  away  the  muscles,  and  observe  that  the  optic  nerve 
gives  off  no  branches,  but  runs  directly  into  the  posterior 
part  of  the  eyeball.  It  is  the  nerve  of  sight. 

Observe  the  tough  outer  coat  (sclerotic  coat)  of  the  eye, 
transparent  over  its  anterior  portion,  where  it  is  called 
cornea.  Looking  at  the  eyeball  from  the  front,  observe 
a  dark  hole  (the  pupil)  through  which  the  light  enters  the 
black-lined  eyeball,  and  around  the  pupil  a  motley  colored 
circular  band  (the  iris) .  If  the  eye  be  cut  open,  the  clear, 
double-convex  crystalline  lens  will  be  found  suspended  in 
the  humors  of  the  eye.  It  is  the  part  which  brings  the 
rays  of  light  to  focus  on  the  terminations  of  the  optic 
nerve,  and  causes  sic 


Other  Cranial  Nerves.  —  Behind  the  optic  nerves,  a 
pair  of  large,  conspicuous  nerves  (the  trigeminal  nerves) 
will  be  seen  extending  forward,  and  sending  off  large 
branches  to  the  upper  jaw,  barbels,  palate,  etc.  Some  of 
its  branches  may  be  easily  traced.  A  pair  of  large 
nerves  arise  from  the  posterior  part  of  the  brain,  and 
extend  posteriorly  into  the  body  cavity.  These  are  the 
vagus  nerves,  whose  branches  have  already  been  seen  dis- 
tributed over  the  anterior  wall  of  the  stomach. 

Between  the  vagus  nerves,  which  extend  posteriorly, 


THE    CATFISH.  173 

and  the  several  pairs,  which,  we  have  seen,  extend  ante- 
riorly, are  one  or  more  pairs  which  extend  laterally,  and 
send  branches  to  a  pair  of  thin-walled  swellings  at  the 
base  of  the  hinder  part  of  the  skull.  These  swellings 
are  the  ear  capsules.  Each  of  these,  if  cut  open,  will  be 
found  to  contain  a  membranous  sac  filled  with  liquid  in 
which  floats  an  ear  bone.  Each  is  an  organ  of  hearing, 
capable  of  being  affected  by  vibrations,  which  are  so 
readily  transmissible  through  water. 

Make  a  drawing  of  the  brain  and  cranial  nerves  in 
place,  as  seen  from  above. 

The  Brain.  —  Cut  off  the  cranial  nerves  half  an  inch 
from  the  brain.  Lift  out  the  brain,  place  it  in  alcohol, 
and  study  to  make  out  its  parts. 

1.  Looking  at  the  dorsal  surface  of  the  brain,  observe 
*a  large,  squarish,  anterior  division  of  softer,  more  satiny 
appearance  than  the  rest,  divided  by  a  shallow  median 
groove  into  two  lateral  halves.     This  is  the  cerebrum,  and 
its  halves  are  the  cerebral  hemispheres. 

2.  Looking   at   the   ventral  surface  of  the  cerebrum, 
observe  two  conical  swellings  at  the  base  of  the  olfactory 
nerves.     These  are  the  olfactory  lobes,  the  foremost  portion 
of  the  brain. 

3.  Close   behind   the    cerebrum   are   the   two   smooth, 
roundish  optic  lobes,  which  are  continued  downward  into 
two  inferior  lobes,  that  are  easily  seen  from  one  side  or  from 
below.     Observe  the  optic  nerves  taking  origin  from  this 
part,  and  crossing  ere  they  leave  the  cranium.    Which  side 
of  the  brain  receives  impressions  through  the  right  eye  ? 

4.  On  the  median  dorsal  line,  close  behind  and  above 
the  optic   lobes,  observe  a  conspicuous,  roundish  single 
portion,  the  cerebellum.     This  part  extends  backward  and 
downward  in  two  posterior  lobes,  which  surround  a  deep 
median  depression,  the  fourth  ventricle. 


174  VERTEBRATES. 

5.  That  portion  of  the  brain  below  and  behind  the 
cerebellum  is  the  medulla.  It  tapers  posteriorly  into  the 
spinal  cord. 

Preserve  this  brain  for  comparison  with  that  of  other 
animals  yet  to  be  studied. 

Muscles  of  Body  Wall.  —  Make  a  longitudinal  cut  close 
beside  the  dorsal  fins,  and  down  to  the  spinal  column. 
Extend  this  incision  backward  to  the  caudal  fin,  and  for- 
ward to  the  pectoral  arch.  Remove  the  great  flap  of  flesh 
thus  partly  freed  from  one  side,  dissecting  it  away  from 
the  ribs  and  from  the  inferior  projections  of  the  vertebrae 
posterior  to  the  ribs.  Observe  the  arrangement  of  the 
white  bands  of  muscles,  of  which  it  is  principally  com- 
posed. 

Separate  two  of  the  vertebrse,  and  find  the  spinal  cord 
extending  longitudinally  through  them. 

Plan  of  Structure.  —  Consider  well  the  arrangement  of 
parts  as  you  have  found  them  in  the  fish.  Here  i"  a  new 
plan  of  structure.  The  hard  parts  (bones)  are  inside, 
and  the  muscles  are  attached  to  prominences  on  their 
exterior.  What  general  arrangement  of  skeleton  and 
muscles  have  you  found  in  the  other  animals  studied? 

The  central  parts  of  the  nervous  system  are  inclosed 
within  a  bony  canal  which  extends  along  the  dorsal  side 
of  the  body.  The  anterior  end  of  this  canal  is  expanded 
into  the  wide  cranium;  the  remainder  of  this  tube  is  the 
neural  canal,  which  extends  backward  through  the  verte- 
brse. The  part  of  the  nerve  center  occupying  the  cranium 
is  called  the  brain ;  the  part  occupying  the  neural  canal 
is  called  the  spinal  cord.  There  are  apertures  throughout 
the  length  of  this  bony  tube  for  the  passage  of  nerves 
outward  through  its  walls  to  all  parts  of  the  body. 

Ventral  to  this  tube  of  bone,  which  holds  and  protects 


THE   CATFISH.  175 

the  central  nervous  system,  is  another  immensely  larger 
tube,  the  body  cavity,  which  contains  the  organs  of  nutri- 
tion and  reproduction.  The  walls  of  this  latter  tube  are 
largely  membranous,  but  they  are  in  part  supported  by 
the  ribs  and  by  the  lower  bones  of  the  skull.  A  trans- 
verse section  of  the  body  of  the  fish,  therefore,  shows  two 
tubes,  one  above  the  other.  How  does  this  arrangement 
of  nerve  center  and  nutritive  organs  differ  from  the 
arrangement  studied  in  insects  ?  In  the  river  mussel  ? 

The  Bony  Skeleton.  —  A  few  points  respecting  the 
structure  and  arrangement  of  the  parts  of  the  bony  skele- 
ton must  be  studied  here.  Use  a  prepared  skeleton  for 
reference,  and  study  the  parts  in  a  disjointed  skeleton, 
which,  if  not  furnished  you,  you  can  easily  prepare  for 
yourself.1 

I.  The  Spinal  Column.  —  Study  the  spinal  column. 
This  is  the  most  important  and  characteristic  part  of 
the  skeleton.  Observe  that  its  constituent  vertebrae  are 
not  all  alike.  Their  differences  are  such  as  to  make  two 
regions  distinguishable  in  the  spinal  column.  The  an- 
terior portion  extending  backward  as  far  as  the  hindmost 
pair  of  ribs  is  the  body  region,  and  the  remaining  posterior 
portion  without  ribs  is  the  tail  region.  Isolate  one  of  the 
middle  vertebrae  of  the  tail  region,  taking  care  not  to 
injure  any  of  the  small  bony  processes  that  arise  from 
it,  and  examine  it.  Observe  a  thick,  solid,  hourglass- 
shaped  central  portion,  concave  on  both  anterior  and 
posterior  faces,  and  perforated  for  the  passage  of  the 
spinal  cord.  This  is  the  centrum  (or  body  of  the  ver- 
tebra). Observe  a  pair  of  processes  arising  from  the 
dorsal  surface,  one  on  either  side  of  the  median  line, 
and  soon  uniting  to  form  a  long,  sharp  neural  spine.  By 
their  union  they  form  an  arch  above  the  centrum,  in  which 

1  For  the  method,  see  Appendix,  p.  287. 


176  VERTEBRATES. 

lies  a  large  artery.  A  similar  pair  of  processes  arise,  and 
unite  in  a.  similar  w.ay  on  the  ventral  surface,  to  form  a 
long  hemal  spine.  Another  large  artery  is  lodged  in  the 
arch  at  the  base  of  this  spine.  Notice  that  both  spines 
are  directed  backward.  Find  four  small  processes  on  the 
anterior  margin,  and  four  on  the  posterior  margin,  of 
the  centrum.  These  are  articulating  processes  (zyga- 
pophyses).  They  join  corresponding  processes  on  adja- 
cent vertebrae,  and  serve  to  hold  the  several  vertebrae 
more  firmly  together.  Study  the  relation  between  these 
processes  in  vertebrae  that  have  not  been  disarticulated. 

Draw  a  vertebra  as  seen  from  one  side,  and  as  seen  from 
one  end. 

II.  Ribs   and    Interneurals.  —  Compare    this    vertebra 
with  others  both  before  and  behind  it  in  the  tail  region. 
Observe  that  in  several  of  the  foremost  vertebrae  of  this 
region  the  large  processes  of  the  ventral  side  do  not  unite 
to  form  a  single  hemal  spine,  but,  diverging,  form  two 
spines.      Proceeding  forward  into  the   body  region,  ob- 
serve  that   there   they   no    longer   form   a  hemal   arch, 
that   they  become   more   and   more  divergent,  and   that 
ribs  are  added  to  their  outer  ends.       Observe  that  the 
articulation   of   each   rib  is   such   that   it  appears  to  be 
spliced  to  the   process  which   supports  it.       How  many 
pairs  of  ribs  are  there?     Observe  that  the  neural  spines 
of  the   rib-bearing  vertebrae  are  reduced  in  length  and 
modified  in  form  to  accommodate  the  bones  which  sup- 
port the  anterior  dorsal  fin.     The  latter  bones,  because 
they  usually  fit  in  between  the  neural  spines,  are  called 
interneurals. 

III.  Spines  and  their  Supports.  —  The  part  of  the  spinal 
column  anterior  to  the  ribs  consists  of  several  vertebrae 
solidly    welded    together,    and    so    greatly   modified    as 
scarcely  to  be  recognized  as  vertebrae  at  all.       They  are 
joined  to  the  long   dorsal  process  from  the  skull  to  the 


THE   CATFISH.  177 

bony  pectoral  arch,  and  to  the  foremost  interneurals,  in 
such  a  manner  as  to  give  a  very  firm,  bony  support  to  the 
three  defensive  spines. 

The  joints  at  the  bases  of  these  spines,  though  not 
characteristic  of  fishes  in  general,  but  a  peculiarity  of  a 
small  group,  show  an  interesting  kind  of  animal  mech- 
anism, and  are  well  worthy  of  an  examination. 

Examine  first  the  attachments  of  the  dorsal  spine.  It 
is  fastened  by  a  ring  to  the  top  of  the  third  interneural. 
The  first  interneural  is  small,  the  second  and  third  inter- 
neurals are  grown  together  solidly  into  one  piece  (the 
buckler),  and  the  notched  tip  of  the  backward  process 
from  the  skull  (the  helmet)  fits  against  the  anterior 
edge  of  this  piece.  The  dorsal  spine  arises  from  the 
third  interneural,  and  a  rudiment  of  another  spine  from 
the  top  of  the  second  interneural.  This  rudiment  is  a 
small,  oval  bone,  forked  below.  It  is  set  against  the  base 
of  the  great  spine  in  front,  and  acts  as  a  sort  of  bolt,  or 
fulcrum  of  support.  The  widened  neural  spines  also  con- 
tribute to  the  support  of  the  great  spine,  as  can  be  readily 
seen. 

Examine  one  of  the  pectoral  spines.  Study  the  beauti- 
ful joint  by  which  it  is  united  to  the  pectoral  arch.  In 
how  many  directions  is  it  movable  ? 

Observe  the  great  strength  and  solidity  of  this  pectoral 
arch,  and  the  comparative  weakness  and  small  size  of  the 
pelvic  arch. 

The  catfish  is  a  representative  of  the  class  Pisces,  or  fishes 
of  the  great  branch  Vertebrata  (or  back-boned  animals). 

Other  Fishes  of  very  different  structure  can  readily 
be  obtained  for  study  in  any  locality.1  A  common 
sucker,  or  a  buffalo  fish,  is  recommended  for  study,  and 

1  Use  Jordan's  Manual  of  the  Vertebrates  for  identifying  the  species  of 
fishes. 

NEED.    ZOOL. 12 


178 


VEETEBRATES. 


for    comparison   with    the    catfish.      Compare   especially 

.vith  regard  to  the  following  points  :  — 

1.  The  shape  of  its  body. 

2.  The  character  of  its  body  covering. 

3.  The  shape  of  its  mouth. 

4.  The  number  and  position  of  bones  bearing  teeth. 

5.  The  character  of  the  gills  and  gill  rakers. 

6.  The  character  of  the  dorsaland  pectoral  fins. 

7.  The  shape  and  attachments  of  the  air  bladder. 

8.  The  foremost  vertebrae  of  the  spinal  column,  etc. 


THE  FROG. 

(Eana.) 

Haunts  and  Habits.  —  In  the   springtime  the   musical 
efforts  of  this  animal  are  a  sufficient  guide  to  the  locali- 

ties to  be  searched  for 
specimens.  In  warm 
weather  small  frogs 
will  be  flushed  from 
their  resting  places  in 
.-A  the  grass  by  walk- 

---._  ing  rapidly  alongside 
any  brook  or  pon(L 

They  may  be  cap- 
tured in  a  stout  net. 
In  cold  weather  live 
specimens  may  be  ob- 
tained from  dealers, 
or  dredged  up  from  the  bottom  of  ponds.  Specimens 
captured  in  autumn  may  be  kept  alive  a  long  time 
without  food,  if  kept  in  a  cool,  damp  place  ;  for  in  the 
winter  season  they  are  normally  inactive,  and  take  no 
food. 


COMMON  FROG  (Rana  virescens). 


THE   FROG.  179 

The  interesting  habits  of  the  frog  should  be  studied  in 
the  field  if  opportunity  offers. 

Study  of  a  Live  Specimen.  —  Study  the  live  frog  in  the 
laboratory.  Observe  :  - 

1.  The  stocky,  humpbacked  body. 

2.  The  absence  of  tail  and  of  fins. 

3.  The  presence  of  well-developed  legs. 

4.  The  presence    of   eyelids.      Touch  the  eye  with  a 
pencil,  and  watch  the  lids.     Are  they  of  one  sort? 

5.  Its  method  of  locomotion  in  water. 

6.  Its  method  of  locomotion  on  land. 

7.  Its  sitting  posture. 

8.  Its  breathing :  what  external  parts  participate? 

Circulation  of  Blood. — Wrap  the  frog  in  a  wet  towel, 
leaving  a  hind  foot  protruding.  Chloroform  it,  and  ex- 
amine with  the  microscope  the  circulation  of  blood  in  the 
web  of  its  foot,  as  directed  for  the  fin  of  a  catfish. 

Structure.  —  Give  additional  chloroform,  and,  when  the 
frog  is  dead,  study  its  structure.  Note  :  — 

1.  The  color  and  markings  of  the  head  and  of  the  body ; 
of  the  dorsal  and  ventral  surfaces. 

2.  The  smooth,  moist,  scaleless  skin. 

3.  The  prominent  eyes,  and  behind  them,  on  the  sides 
of  the  head,  the  round  tympanic  membranes  of  the  ears. 

4.  The  wide  mouth. 

5.  A  pair  of  nostrils  above  the  mouth. 

Open  the  mouth  and  look  into  it.     Observe  :  — 

1.  The  fleshy  lips  which  narrowly  border  the  jaws. 

2.  The  absence  of  teeth  from  the  lower  jaw. 

3.  The  number,  position,  and  arrangement  of  teeth  in 
the  upper  jaw. 

4.  The  long,  fleshy  tongue.     Draw  it  forward,  and  find 
the  point  of  its  attachment. 


180  VERTEBRATES. 

5.  The  mucilaginous  saliva  which  covers  the  tongue. 
When  a  fly,  or  other  insect  suitable  for  food,  comes  near 
enough,  the  frog  darts  out  this  sticky  tongue,  and  draws 
the  entangled  fly  into  its  mouth. 

Pass  a  bristle  into  the  nostrils  from  the  outside,  and 
discover  where  they  open  into  the  mouth. 

Cut  a  hole  in  the  tympanic  membrane,  and  insert  a 
bristle  into  the  cavity  it  covers,  and  push  the  bristle  into 
the  mouth.  The  wide  tube  by  which  it  enters  the  mouth 
is  the  Eustachian  tube. 

The  posterior,  funnel-shaped  part  of  the  cavity  seen  on 
looking  into  the  mouth  is  the  pharynx.  Its  folded  walls 
converge  toward  the  esophagus. 

On  the  floor  of  the  pharynx  is  a  narrow  slit  which 
leads  into  the  trachea,  and  thence  to  the  lungs.  Pass  a 
bristle  into  this  slit. 

Find  a  small,  isolated  patch  of  teeth  on  the  roof  of  the 
mouth. 

Dissection.  —  Dissect  the  frog  under  water.  A  pre- 
pared skeleton  should  be  at  hand  for  reference  in  locating 
bony  parts. 

Cut  through  the  skin  along  the  median  ventral  line, 
from  the  mandible  to  the  posterior  end  of  the  body. 
Make  a  second  cut  at  right  angles  to  the  first,  entirely 
across  the  middle  of  the  ventral  surface,  and  turn  back 
the  four  flaps  of  skin  thus  formed.  This  will  expose  the 
thin,  muscular  abdominal  wall.  Observe  a  dark  vein 
showing  through  the  abdominal  muscle  on  the  median 
line.  Make  a  longitudinal  cut  through  the  body  wall, 
a  little  to  one  side  of  the  median  line,  so  as  to  avoid 
injuring  this  vein,  and  continue  the  cut  forward  to  the 
bony  pectoral  arch,  or  shoulder  girdle.  Then  consult  a 
skeleton,  to  see  how,  by  cutting  to  one  side  of  the  median 
line,  you  may  avoid  injuring  the  elongated  median  bone 


THE   FROG.  181 

of  this  girdle.  Continue  the  cut  forward  to  the  base  of  the 
tongue.  Stretch  the  fore  legs  out  at  right  angles  to  the 
body,  and  pin  them  so.  Turn  back  the  edges  of  the  last 
incision,  and  fully  expose  the  organs  of  the  body  cavity. 

Internal  Features.  —  Perhaps  the  most  conspicuous  of 
the  internal  organs  is  the  large,  mottled  reddish  liver, 
which  consists  of  a  large  double  lobe  on  the  right  side 
of  the  body,  and  of  a  smaller  single  lobe  on  the  left  side. 
Immediately  in  front  of  the  liver  is  the  heart,  inclosed  in 
a  thin,  transparent  sac,  the  pericardium.  If  the  heart  is 
still  beating,  the  arterial  system  should  be  injected.1 

Pinch  up  the  pericardium  with  forceps,  and  cut  it  away 
with  sharp  scissors.  Cut  away  also  its  attachments  to 
the  body  wall,  taking  great  care  not  to  cut  any  blood 
vessels  or  other  organs. 

Pass  a  pipette  or  blowpipe  through  the  mouth,  into 
the  trachea,  and  inflate  the  lungs  to'  see  their  size  and 
position. 

I.  Digestive  Organs.  —  Pass  a  long  probe  through  the 
mouth  and  pharynx  into  the  esophagus,  and  thence  back- 
ward into  the  long,  white  stomach,  which  lies  just  behind, 
or  partly  concealed  by,  the  liver.  From  the  posterior  end 
of  the  stomach  trace  the  intestine.  It  turns  forward, 
downward,  backward,  then  forms  a  spire  on  the  right  side 
of  the  body,  and  then,  returning  to  the  median  line, 
enters  an  expanded  terminal  portion,  the  cloaca.  Ducts 
from  the  reproductive  and  renal  organs  also  enter  this 
chamber.  Observe  the  mesentery  with  which  the  intes- 
tine is  invested,  and  through  which  its  blood  vessels  pass. 
The  position  of  the  liver  has  been  noticed :  find  the 
greenish  gall  bladder  attached  to  one  of  its  lobes,  and  find 
a  duct  leading  from  the  gall  bladder  to  the  intestine. 
This  duct  will  usually  be  made  more  evident  by  squeezing 

1  For  the  method,  see  Appendix,  p.  285. 


182  VEKTEBRATE& 

the  contents  of  the  gall  bladder  out  into  ito  The  pale 
or  whitish  compact  mass  lying  between  the  stomach,  in- 
testine, and  liver,  is  the  pancreas.  What  is  the  relation 
between  this  organ  and  the  duct  of  the  gall  bladder  ? 

IL  Reproductive  Organs.  —  A  pair  of  digitate,  yellow 
fatty  bodies  are  attached  to  the  dorsal  wall  of  the  body 
cavity,  behind  the  stomach,  and  close  beside  the  median 
line.  The  paired  reproductive  organs  lie  just  poste- 
rior to  these,  —  rounded  yellow  testes  in  the  male  ;  and 
folded  or  lobed,  lighter  colored  ovaries  in  the  female. 
In  the  breeding  season,  the  ovaries  may  be  found  so 
distended  with  eggs  as  to  fill  out  most  of  the  body  cavity. 
The  oviducts,  which  convey  the  eggs  to  the  cloaca,  are 
very  long  and  much  convoluted  tubes,  having  no  connec- 
tion with  the  ovary,  but  opening  by  a  funnel-shaped 
orifice  into  the  body  cavity  near  the  esophagus. 

III.  Renal  Excretory  Organs. — A  pair  of  reddish  brown 
kidneys  lie  on  the  dorsal  side  of  the  body  cavity,  near  the 
cloaca;    and  ducts  from  these  pass  to  the  large,  white, 
bilobed  urinary  bladder,  which  occupies  the  extreme  pos- 
terior end  of  the  body  cavity,  and  which,  when  found 
empty,  presents  a  crumpled  appearance = 

The  small,  roundish  red  body,  dorsal  to  the  cloaca,  arid 
near  the  anterior  end  of  the  kidneys,  is  the  spleen. 

IV.  Circulatory  Organs.  —  The  central  organ  of  circu- 
lation in  the  frog  is  the  heart.     In  it  find  three  divisions,— 
a  firm  muscular,  conical  posterior  division,  the  ventricle; 
and  two  anterior,  thin-walled  divisions,  auricles.    A  cylin- 
drical arterial  trunk  arises  from  the  anterior  end  of  the 
ventricle,  and  passes  obliquely  forward  across  the  upper- 
most   ventricle,    and    soon    divides    into    two    principal 
branches. 

Now  trace  the  principal  arteries  and  veins.  If  the 
arterial  system  has  been  injected,  there  will  be  no  diffi- 
culty in  distinguishing  between  arteries  and  veins ;  if  not, 


THE   FROG,  183 

the  arteries  may  usually  be  distinguished  by  their  firmer 
walls  and  somewhat  lighter  color.  No  visible  blood  vessels 
should  have  been  severed  up  to  this  point  in  the  dissec- 
tion. Begin  with  the  venous  system,  and  find  the  prin- 
cipal avenues  by  which  the  blood  is  returned  to  the  heart, 
after  being  distributed  throughout  the  tissues.  Find 
again  the  vein  that  was  seen  through  the  thin  abdominal 
wall  before  the  body  cavity  was  cut  open.  Trace  this 
vein  backward  far  enough  to  see  the  large  branches  com- 
ing up  from  the  hind  legs.  Trace  it  also  forward.  Ob- 
serve that  it  soon  leaves  the  body  wall,  and  descends 
through  the  body  cavity  to  the  liver,  where  it  branches, 
sending  one  branch  to  each  lobe  of  that  organ.  This  is 
the  ventral  route  to  the  liver  ;  there  is  also  a  dorsal  route 
through  the  kidney.  Turn  the  organs  that  cover  the 
kidney  over  to  one  side,  and  find  a  longitudinal  vein  com- 
ing from  the  posterior  end  of  the  body  cavity,  and  passing 
along  the  external  margin  of  the  kidney,  and  dividing  up 
into  numerous  branches,  which  enter  the  mass  of  the 
kidney.  Then  find  a  corresponding  set  of  venous  branch- 
lets  coming  from  the  inner  side  of  the  kidney,  meeting 
branchlets  from  the  other  kidney,  and  uniting  into  another 
large  vein,  which  proceeds  forward  to  the  liver,  receiving 
important  branches  from  the  viscera  at  several  points. 
This  is  the  portal  vein.  Trace  it  to  the  liver.  Then 
draw  the  liver  backward,  and  turn  the  ventricle  over  for- 
ward, and  see  the  single  large  vein,  the  postcava,  which 
conveys  the  blood  from  the  liver  into  the  venous  sinus, 
and  thence  into  the  right  auricle.  Draw  the  heart  gently 
backward,  and  see  the  two  large  veins  (prcecavce),  which 
bring  the  blood  into  the  same  chamber  from  the  anterior 
parts  of  the  body.  The  blood  flows  from  the  auricle 
into  the  ventricle,  and  is  forced  out  again,  by  the  con- 
traction of  the  ventricle,  through  the  arterial  trunk. 
Trace  now  its  outward  course.  The  arterial  trunk 


184  VERTEBRATES. 

divides  into  two  branches,  each  of  which  is  made  up  of 
three  aortic  arches,  which,  curving  dorsally,  go  a  little 
way  together,  bound  up  in  a  mass  of  fatty  and  connective 
tissue-  Carefully  dissect  away  this  tissue,  and  disclose 
the  three  arches  of  one  side.  The  anterior  (carotid}  arch 
first  leaves  its  fellows,  and  at  once  divides  into  two 
branches  which  go  to  the  head.  The  posterior  (pulmo- 
cutaneous)  arch  sends  branches  to  the  lung  and  to  the 
skin.  The  larger  middle  aortic  arch  curves  dorsally  and 
posteriorly.  Lift  the  stomach  and  adjacent  organs  a 
little  away  from  the  dorsal  wall,  and  see  this  middle  arch 
extending  backward,  and  uniting  with  its  fellow  of  the 
opposite  side  on  the  median  line.  Observe  that  the  single 
dorsal  aorta  thus  formed  gives  off  at  once  a  very  large 
branch  to  the  organs  of  the  body  cavity,  itself  extends 
posteriorly  along  the  dorsal  wall,  and  finally  divides  into 
the  two  iliac  arteries,  which  go  to  the  hind  legs. 

Trace  now  the  three  arches  of  one  side  back  to  their 
origin.  Cut  each  off  at  the  point  of  its  separation  from 
its  fellows,  and  pass  into  it  a  bristle.  Then  with  fine 
scissors  lay  each  one  open,  cutting  backward  toward  the 
ventricle.  Compare  the  aortic  arches  of  the  frog  with 
those  of  the  catfish. 

That  the  hindmost  aortic  arch  conveys  blood  to  the  lung 
for  aeration  has  already  been  noticed.  From  the  lung  a 
pulmonary  vein  conveys  the  aerated  blood  back  to  the 
left  auricle  of  the  heart,  whence  it  passes  into  the 
ventricle,  to  be  mixed  with  the  venous  current  from 
the  right  auricle, 

V.  Respiratory  Organs,  —  Cut  the  vein  and  artery  con- 
necting each  lung  with  the  vascular  system,  arid  trace  the 
lungs  forward  to  their  union  in  the  trachea.  Dissect  out 
the  trachea,  and  trace  it  forward  to  the  mouth.  Observe 
that  it  passes  through  a  notch  between  two  posterior  horns 
of  a  broad,  flat  cartilage  in  the  floor  of  the  mouth,  the 


THE   FROG.  185 

hyoid  cartilage.     Lay  open  the  anterior  part  of  the  trachea, 
and  note  the  structure  of  its  walls. 

Again  inflate  the  lungs  through  the  trachea,  and  study 
their  structure.  Observe  that  they  are  composed  of  rela- 
tively few  and  large  air  cells  (or,  more  properly,  air 
spaces),  and  that  the  walls  of  these  do  not  afford  a  very 
great  area  over  which  the  blood  can  be  distributed  for 
aeration.  The  distribution  of  the  capillaries  in  the  skin 
is  such  as  to  bring  the  blood  near  enough  to  the  surface 
for  partial  aeration  there.  But  the  total  supply  of  oxy- 
gen obtained  from  both  sources  is  relatively  small,  and 
would  be  inadequate  to  any  but  a  cold-blooded,  sluggish 
animal. 

The  Nervous  System.  —  Turn  the  organs  of  the  body 
cavity  gently  to  one  side  until  the  spinal  column  is 
visible.  Observe  the  white  spinal  nerves  extending  out 
from  it,  along  the  body  wall,  just  beneath  the  smooth, 
transparent  peritoneum.  Observe  that  each  spinal  nerve, 
near  its  origin,  sends  a  branch  ventrally  into  the 
body  cavity  to  meet  a  very  delicate  nerve  cord  that  ex- 
tends longitudinally,  ventral  to  the  spinal  column,  and 
near  the  median  plane  of  the  body.  Examine  this  nerve 
cord  carefully  with  a  lens  to  find  minute  ganglionic  swell- 
ings on  it  at  its  junctions  with  the  branches  of  the  spinal 
nerves.  Find  also  minute  nerves  arising  from  its  gan- 
glia, and  extending  to  the  internal  organs.  Trace  it  for- 
ward to  the  head.  Find  another  similar  nerve  cord  on  the 
other  side  of  the  median  plane.  Find  minute  white  com- 
missural  nerves  connecting  the  ganglia  of  the  two  chains. 

This  double  series  of  ganglia,  with  connecting  commis- 
sures and  radiating  fibers,  included  within  the  body  cavity 
and  distributed  to  the  nutritive  organs,  constitutes  the 
sympathetic  system.  The  cerebro-spinal  system  consists  of 
brain  and  spinal  column  and  radiating  nerves. 


186  VERTEBRATES. 

I-  Spinal  Nerves.  —  Cut  off  the  esophagus  near  its 
origin,  and  remove  the  viscera.  Note  the  absence  of  ribs 
from  the  walls  of  the  body  cavity..  Make  out  ten  pairs 
of  spinal  nerves,  as  follows  :  — 

The  nerves  of  the  first  pair  curve  ventrally  and  ante- 
riorly, and  are  distributed  to  the  lower  jaw. 

The  nerves  of  the  second  and  third  pairs  unite,  and  go 
to  the  fore  legs.  The  nerves  of  the  second  pair  are  large 
and  conspicuous,  and  extend  laterally  at  right  angles  to 
the  spinal  column  :  those  of  the  third  pair  are  smaller, 
and  bend  anteriorly  to  meet  those  of  the  second.  The 
two  again  divide  and  reunite  repeatedly,  to  form  a  plexus 
(the  brachial  plexus). 

The  nerves  of  the  fourth,  fifth,  and  sixth  pairs  extend 
laterally  and  posteriorly,  to  be  distributed  to  the  body 
wall. 

The  nerves  of  the  seventh,  eighth,  and  ninth  pairs  go 
to  the  hind  legs.  They  unite  to  form  a  plexus  (the  ilio- 
sacral  plexus),  which  terminates  in  the  large  sciatic  nerve 
of  the  thigh. 

The  nerves  of  the  tenth  pair  are  very  small.  They 
may  be  seen  close  beside  the  posterior  end  of  the  spinal 
column. 

II.  The  Brain.  —  Remove  the  skin  from  above  the 
cranium  and  from  one  side  of  the  head.  Dissect  it  free 
from  the  tympanic  membrane  with  great  care.  Cut 
away  the  bony  roof  of  the  cranium,  and  with  a  gentle 
stream  of  water  from  a  pipette  wash  out  the  soft  sub- 
stance that  covers  the  brain  and  fills  out  the  cavity. 
Make  out  the  following  parts  :  — 

1.  A  pair  of  conical  olfactory  lobes,  extending  forward 
from  the  extreme   anterior  end,   and   tapering   into   the 
olfactory  nerves. 

2.  Immediately  behind  these,  the  large,  white,  cerebral 
hemispheres,  which  make  up  the  cerebrum. 


THE   FROG.  187 

3.  Behind  these  are   a   pair   of   conspicuous   rounded 
eminences,  well  marked  off  from  each  other,  and  from  the 
other  parts.     These  are  the  optic  lobes.     The  large  optic 
nerves  arise  from  these  below,  and  cross  each  other  before 
going  to  the  eyes. 

4.  Behind  the  optic  lobes,  and  on  the  median  line,  is  a 
deep  depression,  the  fourth  ventricle.     It  is  covered  over 
with  a  thin  plexus  of  blood  vessels,  which  is  easily  stripped 
off,  and  is  often  torn  away  with  the  cranial  wall.     In  front 
of  the  ventricle,  and  behind  the  optic  lobes,  is  a  single 
transverse  band  of  nervous  tissue.     This  is  the  cerebellum. 
The  nervous  mass  which  surrounds  the  ventricle  on  the 
sides   and   below  is  the  medulla.     It  tapers   posteriorly 
into  the  spinal  cord. 

5.  There  remains  a  portion  of  the  brain  between  the 
cerebral  hemispheres  and  the  optic  lobes  which  has  not 
yet  been  mentioned.     It  is  the  midbrain.      From  its  dor- 
sal  surface,  between   the   posterior  ends  of   the  cerebral 
hemispheres,    and   on   the   median    line,    arises    a   single 
rounded  prominence  which  is  not  composed  of  nervous 
tissue.     It  is  the  pineal  gland. 

6.  About  eight  pairs  of  nerves  arise  from  the  ventral 
surface  of  the  medulla :  these  are  small,  and  exceedingly 
difficult  to  trace.     The  fifth  and  tenth  cranial  nerves  are 
largest,  and  have  each  a  ganglion  not  far  out  from  their 
origin.     These  ganglia  are  each  connected  with  forward 
prolongations  from  the  longitudinal  commissures  of  the 
sympathetic  system. 

7.  The  fact  that  the  single  cavity  that  has  been  seen  in 
the  brain  thus  far  is  called  the  fourth  ventricle,  will  sug- 
gest that  there  are  others.     Two  others  will  be  exposed 
by  cutting  a  horizontal  slice  from  the  top  of   the  cere- 
brum :    these   are  the  two  lateral   ventricles  of   the  fore- 
brain.     They  occupy  the  cerebral  hemispheres,  and  unite 
posteriorly  around  a  median  septum.     The  cavity  formed 


188  VERTEBRATES. 

by  their  union  is  continued  posteriorly  into  the  midbrain, 
and  expands  there  into  a  narrow  cavity,  extending  ob- 
liquely upward  and  downward,  the  third  ventricle.  A 
narrow,  median  canal,  the  iter,  connects  the  third  and 
fourth  ventricles.  A  pair  of  round  cavities,  the  optic 
ventricles,  occupy  the  optic  lobes,  and  are  connected  with 
the  iter.  If  the  brain  be  turned  to  one  side,  and  drawn 
upward  out  of  the  cranium  a  little,  there  may  be  seen  a 
downward  prolongation  from  the  midbrain  toward  the 
roof  of  the  mouth.  It  is  the  pituitary  body. 

If  the  foregoing  points  in  the  study  of  the  brain  have 
not  been  made  out  satisfactorily  in  a  fresh  specimen,  place 
a  frog's  head  a  few  days  in  alcohol  to  harden,  and  with  it 
try  again. 

The  Ear.  —  In  the  ear  observe  the  tympanum,  from 
which  the  skin  has  been  removed.  Observe  the  opaque 
spot  in  it,  and  the  surrounding  transparent  area.  The 
opaque  spot  is  the  point  of  attachment  of  an  elastic  rod 
which  extends  across  the  cavity  inside,  and  communicates 
with  the  inner  ear.  When  sound  waves  fall  on  the  tym- 
panum, and  cause  it  to  vibrate,  its  vibrations  are  carried 
through  the  elastic  rod  to  the  inner  ear,  which  is  the  true 
organ  of  hearing,  and  which  is  securely  lodged  within  the 
bone  of  the  skull.  Dissect  out  this  elastic  rod.  It  is 
called  the  columella.  It  is  sometimes  partly  ossified  in 
the  middle. 

Appendages.  —  That  there  are  two  pairs  of  legs  will 
have  been  noticed  already.  Which  pair  is  most  service- 
able in  locomotion?  What  peculiarity  in  its  structure 
would  indicate  that  a  frog  could  jump  well,  were  its 
habits  entirely  unknown?  What  other  animals  have  you 
seen  having  the  same  peculiarity  of  structure,  and  corre- 
sponding ability  to  jump  ? 

In  fore  and  in  hind  leg  find  three  principal  divisions,  — 


THE   FROG.  189 

in  the  fore  leg,  named  from  the  body  outward,  arm,  fore- 
arm, and  hand  (for  this  limb  is  homologous  with  the 
upper  limb  or  arm  of  man)  ;  and  in  the  hind  leg,  thigh 
(QY  femur),  shank,  and  foo t. 

Make  drawings  of  both  hand  and  foot  as  seen  from 
above.  Compare  the  two  as  to  the  number  of  digits  or 
phalanges  in  each,  and  the  number  of  joints  in  each  digit. 
In  the  males  the  base  of  the  inner  digit  of  each  hand  is 
greatly  swollen  in  appearance.  Such  a  peculiarity  of  sex, 
occurring  entirely  apart  from  the  sexual  organs,  is  called 
a  secondary  sexual  character. 

Study  of  Superficial  Leg  Muscles. — Cut  the  skin  around 
the  base  of  one  of  the  hind  legs,  dissect  it  free  from  the 
underlying  muscles  half  the  length  of  the  thigh,  and  then 
strip  it  off  over  the  foot  like  a  stocking,  wrong  side  out. 
Now  study  the  arrangement  of  parts  in  this  extremity. 
The  whitish  muscles  now  cover  all  other  parts.  Dissect 
apart,  without  freeing  at  their  ends,  several  of  the  large 
muscles  on  the  back  of  the  femur,  and  find  nerves  and 
blood  vessels  and  bone.  Free  at  its  edges  the  large  muscle 
(gastrocnemius)  of  the  back  of  the  shank,  and  observe  :  — 

1.  The   connective  tissue  enveloping  all  the  muscles, 
and  binding  them  together. 

2.  The  connective  tissue  sheath  enveloping  each  indi- 
vidual muscle. 

3.  The   white,    strong   tendon,   in   which   this    muscle 
terminates  at  its  outer  end.     Follow  this  tendon  (tendo 
AcMllis)  outward,  along  the  sole  of  the  foot,  and  see  it 
dividing,  and  its  divisions  coalescing  with  the  tendons  of 
other  shorter  muscles  of  the  foot,  and  extending  to  the 
toes.     Pull  this  tendon  toward  the  body,  and  observe  the 
effect  on  the  foot. 

4.  The  close  attachment  of  the  inner  end  of  this  muscle 
at  the  back  of  the  knee  joint. 


190  VERTEBRATES. 

Three  terms  which  apply  to  muscles  need  to  be  learned  : 
(1)  the  thick,  swollen  central  part  is  called  the  belly  of 
the  muscle;  (2)  that  end  of  the  muscle  which  is  most 
fixed  in  position,  and  toward  Avhich,  when  it  contracts, 
the  muscle  pulls,  is  called  its  origin;  (3)  the  attachment 
of  its  other,  freer  end  is  called  its  insertion. 

Relations  of  Muscles,  Blood  Vessels,  and  Nerves.  — 
Dissect  away  the  large  muscles  of  the  thigh  and  shank 
by  cutting  transversely  through  the  belly  of  each,  and  dis- 
secting each  way,  so  as  to  find  the  origin  and  insertion  of 
each,  and  having  care  not  to  cut  blood  vessels  or  nerves. 
Trace  the  great  sciatic  nerve  of  the  thigh.  Follow  its  two 
principal  branches  down  into  the  foot.  Find  and  dis- 
tinguish two  large,  branching  blood  vessels  in  the  thigh, 
the  femoral  artery  and  vein.  This  dissection,  if  thought- 
fully performed,  will  enable  you  to  answer  the  following 
questions :  — 

1.  Where,  with  reference  to  the  joints,  are  the  thickest 
portions  of  the  leg  ? 

2.  What  give  these  points  their  thickness  ? 

3.  What  advantage  is  there  in  the  tendonous  termina- 
tions of  the  muscles  at  the  joints  ? 

4.  Where  are  the  bones  thickest  ? 

5.  What  are  the  ridges  on  the  bones  for  ? 

6.  Which  lie  deeper  in  the  muscles,  arteries  of  veins  ? 

7.  Why  are  the  principal   nerves  so  remote  from  the 
surface  ? 

8.  Why  are  the  insertions  of  these  muscles  all  at  their 
outer  ends  ? 

Separate  the  thigh  and  the  shank  at  the  knee  joint,  and 
observe  the  firm,  white,  elastic  cartilage  forming  the 
articulating  surface. 

Dermis  and  Epidermis.  —  After  the  skin  has  been  lying 
in  water  for  half  a  day,  observe  that  there  is  an  outer 


THE   FROG.  191 

layer  (epidermis)  in  it,  which  tends  to  peel  off  from  the 
thicker  and  vascular  lower  layer  (dermis). 

Study  of  the  Skeleton.  —  With  a  prepared  skeleton  at 
hand  for  reference,  study  the  separate  parts  of  a  disarticu- 
lated skeleton. 

First,  note  the  arrangement  of  parts  in  the  skeleton  : 
the  central,  vertebral  axis,  terminated  in  front  by  the 
skull,  and  supported  by  two  bony  arches  and  two  pairs 
of  jointed  appendages. 

I.  The  Spinal  Column.  —  In  the  spinal  column  find  ten 
separate  vertebrae,  and  a  long,  unsegmented  terminal  por- 
tion (the  urostyle). 

Note  the  presence  of  a  double  row  of  stout  lateral  pro- 
cesses, and  the  absence  of  ribs.  How  many  of  the  vertebrae 
bear  lateral  processes  ?  Why  are  the  lateral  processes  of 
the  third  and  ninth  vertebrae  stronger  than  the  others  ? 

Above  the  bases  of  the  lateral  processes  note  the  articu- 
lating processes  (zygapophyses),  and  their  method  of 
uniting  adjacent  vertebrae. 

On  either  side  of  the  spinal  column  observe  the  row  of 
large  openings  through  which  the  spinal  nerves  emerge. 
What  is  the  position  of  one  of  these  openings  in  relation 
to  the  vertebrae  nearest  it  ? 

Isolate  one  of  the  midvertebrae,  and  in  it  see  :  — 

The  large,  central  neural  canal. 

Ventral  to  this,  the  relatively  small  centrum  (or  body 
of  the  vertebra),  with  its  anterior  face  concave,  and  its 
posterior  face  convex. 

Two  stout  pedicels  of  bone,  arising  dorsolaterally  to 
support  the  arch  of  the  neural  canal,  and  bearing  (1) 
the  single  pair  of  stout  lateral  processes,  and  (2)  the  two 
pairs  of  articulating  processes  already  noticed,  and  (3)  on 
the  median  dorsal  line  a  short  neural  spine.  Draw. 

Compare  this  vertebra  with  a  typical  vertebra  of  a  fish. 


192  VERTEBRATES. 

II.  Bones  of  the  Fore  Limb.  —  In  the  fore  limb  find  the 
following  parts  :  — 

The  single  long  bone  of  the  arm,  the  humerus.  Its  shape 
is  characteristic  of  long  bones;  therefore  note  that  it  is 
somewhat  cylindrical,  that  it  is  hollow,  and  that  it  has  an 
expanded  articular  surface  at  each  end,  with  a  shaft  between. 

The  bone  of  the  forearm,  made  up  of  two  bones,  radius 
and  ulna,  which  are  grown  together  (anchylosed). 

In  the  bones  of  the  hand,  three  series  may  be  distin- 
guished :  — 

1.  A  series  of  very  small,  irregularly  shaped,  carpal 
bones,  immediately  succeeding  the  bones  of  the  forearm. 

2.  A  single  transverse  row  of  cylindrical  metacarpal 
bones. 

3.  Several  transverse  and  unequal  rows  of  phalangeal 
bones,  or  phalanges,  growing  successively  shorter  toward 
the  tips  of  the  digits. 

III.  The  Shoulder  Girdle.  —  Study  the  pectoral  arch,  or 
shoulder  girdle.     Observe  that  its  bones,  together  with 
their  attached  cartilages,  form  an  incomplete  ring  around 
the  body,  that  the  two  halves  of  the  girdle  meet  on  the 
median  ventral  line,  and  that  the   parts   are   obviously 
arranged  for  the  support  of  a  pair  of  limbs. 

Observe  that  each  half  of  the  shoulder  girdle  is  com- 
posed (essentially)  of  three  bones,  which  meet  around  the 
cavity  (glenoid  fossa)  into  which  the  head  of  the  humerus 
fits.  One  of  these  bones  (the  scapula)  extends  dorsally, 
and  is  supplemented  by  a  broad  cartilage  on  the  dorsal 
surface.  The  other  two  extend  ventrally  to  meet  their 
fellows  of  the  opposite  side  on  the  median  ventral  line. 
The  larger  posterior  one  is  the  coracoid.  The  slender, 
anterior  one  is  the  clavicle. 

Posterior  to  the  point  of  union  of  the  two  coracoids, 
a  flat  bone  (the  sternum),  which  does  not  belong  to  the 
shoulder  girdle,  extends  posteriorly  on  the  median  ventral 


THE   FROG.  193 

line  ;  and  a  corresponding  bone  (the  omosternum)  extends 
anteriorly  from  the  point  of  union  of  the  two  clavicles. 

What  attachment  is  there  between  the  shoulder  girdle 
and  the  spinal  column  ? 

IV.  Bones  of  the  Hind  Limb.  — The  bones  of  the  hind 
limb  are  as  follows  :  — 

1.  The  single  bone  of  the  thigh  is  the  femur. 

2.  The  bone  of  the  shank  is  the  os  cruris.     It  is  made 
up  of  two  bones,  tibia  and  fibula,  as  indicated  by  the  lon- 
gitudinal grooves  near  its  ends. 

In  the  bones  of  the  foot,  three  series  may  be  distin- 
guished, of  which  the  first  consists  of  two  long,  curved 
tarsal  bones,  united  at  their  cartilaginous  tips.  The  other 
two  series  are  called  metatarsal  and  phalanges,  and  corre- 
spond in  position  and  appearance  to  homologous  parts  of 
the  hand. 

V.  The  Pelvic  Girdle.  —  Study  the  pelvic  girdle.     Ob- 
serve its  shape,  position,  and  attachment  to  the  spinal 
column.     Its  halves  are  very  solidly  welded  together  on 
the  median  line.     Each  half  is  composed  of  three  bones, 
united  about  the  socket  (acetabulum),  into  which  the  head 
of  the  femur  fits ;  and  the  bones,  though  solidly  coherent, 
may  be  distinguished  by  examining  the  lateral  surface  at 
their  point  of  union.     (1)  The  long  bone  extended  ante- 
riorly to  meet  the  lateral  process  from  the  ninth  vertebra, 
and  shaped  like  an  inverted  sled  runner,  is  the  ilium. 
(2)    The  bone  that  forms  the  ventral  fifth  of  the  socket 
(acetabulum),  and,  with  its  fellow,  forms  the  ventral  ridge 
of  the  pelvic  girdle,  is  the  pubis.     (3)    The  bone  that 
forms  the  posterior  two  fifths  of  the  socket,  and,  with 
its  fellow  of  the  opposite  side,  forms  the  posterior  ridge 
of  the  girdle,  is  the  ischium. 

Compare  now  shoulder  and  pelvic  girdle,  and  fore  and 
hind  limb,  and  note  the  principal  points  of  likeness  and 
of  difference  between  them. 

NEED.  ZOOL. 13 


194 


VERTEBRATES. 


VI.  The  Skull.  —  The  study  of  the  vertebrate  skull  is 
well  begun  with  the  skull  of  the  frog,  which  is  wide  and 
open,  and  in  which  all  the  bones  can  be  seen  from  the 
outside. 

Observe  its  triangular  outline  as  seen  from  above,  and 
the  large  orbital  and  nasal  apertures.  Observe  the  pos- 
terior opening  into  the  cranium  (foramen  magnum),  and 
the  pair  of  smooth,  articular  surfaces  (occipital  condyles) 


pmx 


SKULL  OF  BULLFROG  (Rana  catesbiana),  dorsal  view:  pmx,  premaxilla; 
v,  vomer;  mx,  maxillary;  n,  nasal;  g,  girdle  bone  or  sphenethmoid ; 
pf,  parietof rontal ;  ptg,  pterygoid;  po,  prootic;  sq,  squamosal;  qj,  quad- 
ratojugal;  o,  occipital  region  surrounding  the  foramen  magnum. 

close  beside.     These  meet  corresponding  surfaces  on  the 
anterior  end  of  the  first  vertebra. 

The  bones  composing  the  skull  are  as  follows :  — 

1.  The  bone  which  forms  the  back  of  the  brain  case, 
and  immediately  surrounds  the  foramen  magnum,  is  the 
occipital. 

2.  The  stout  pillar  of  bone,  which  extends  laterally  at 
the  base  of  the  skull  at  right  angles  to  the  median  line, 
is  the  pro  otic,  so  called  because  it  lies  in  front  of  and  covers 
the  capsule  of  the  inner  ear. 


THE   FROG.  195 

3.  The  hammer-shaped  bone,  which  rests  on  the  outer 
edge  of  the  prootic,  and  extends  its  "  handle "  down  to 
the  posterior  angle  of  the  lower  jaw,  is  the  squamosal. 

4.  On  the  dorsal  surface,  three  pairs  of  bones  in  front 
of  the  occipital  meet  on  the  median  line.      The  first  pair 
consists  of  two  long,  narrow  bones,  which  cover  almost 
the  whole  cranium.     These  are  the  parietofrontals. 

5.  In  front  of  the  last  lies  a  pair  of  triangular  nasals. 

6.  In   front   of   the  nasals   is  a  pair  of   smaller  bones 
(premaxillaries)  which  form  the  tip  of  the  snout,  which 
bear  teeth,  and  which  send  narrow  processes   backward 
toward  the  nasals. 

7.  The   border   of  the   lower   jaw   is   formed  by  the 
mandible,  which  consists  of  two  rami  (or  branches)  which 
meet  on  the  median  line  in  front. 

8.  The  greater  part  of  the  border  of  the  upper  jaw  is 
formed  by  a  maxillary  bone  on  either  side,  bearing  abun- 
dant teeth. 

9.  Between  the  posterior   end  of   maxillary   and   the 
"  handle  end  "  of  the  squamosal  is  a  small  bone  (the  quad- 
ratojugal~)  which  completes  the  border  of  the  upper  jaw. 

10.  Looking  at  the  ventral  surface  of  the  skull,  a  con- 
spicuous T-shaped  bone  is  seen  extending  along  the  floor 
of  the  cranium.     It  is  the  parasplienoid. 

11.  At  its  anterior  end,  a  girdle  bone  (the  sphenethmoid) 
surrounds  the  anterior  third  of  the  brain  case. 

12.  Two  slender  palatines  extend  transversely  outward 
to  the  maxillaries  on  either  side.     These  lie  ventral  to  the 
posterior  border  of  the  nasals. 

13.  Between  the  palatines  and  the  premaxillaries  are  a 
pair  of  irregular  vomers,  each  with  a  posterior  process  bear- 
ing teeth. 

14.  Lying  just  within  the  posterior  angle  of  each  jaw, 
as  seen  from   below,  is  a  conspicuous,  three-rayed   bone 
(the  pterygoid). 


196  VERTEBRATES. 

The  cranium  is  of  cartilage  when  first  formed,  and  is 
not  completely  ossified  in  old  specimens,  as  may  be  seen 
from  the  large  spaces  left  in  its  lateral  walls  in  prepared 
skeletons. 

Make  an  enlarged,  and  if  necessary  diagrammatic,  draw- 
ing of  the  frog's  skull  as  seen  from  below,  naming  all  the 
bones  visible  in  the  drawing. 

Development.  —  Every  student  should  study  the  life 
history  of  the  frog.  In  the  spring  the  eggs  may  be  easily 
obtained  from  shallow  pools  in  which  frogs  are  heard 
croaking.  Being  as  large  as  peas,  and  each  with  a  dark- 
colored  yolk  surrounded  by  a  layer  of  whitish  albumen, 
and  all  suspended  in  large  lumps  of  transparent,  jelly-like 
substance,  they  are  conspicuous  and  peculiar  appearing 
objects.  They  may  be  looked  for  at  the  edges  of  the 
pools,  amid  the  trash  which  collects  there,  and  often  partly 
hidden  by  it.  These  egg  masses  are  popularly  known  as 
frog  spawn. 

The  eggs,  if  carried  home  or  to  the  laboratory,  and 
kept  in  clean,  cool  water,  will  go  on  developing.  If 
freshly  laid  eggs  have  been  obtained,  segmentation  may 
be  seen  taking  place  in  the  yolk.  Later,  as  the  embryo 
develops,  the  yolk  will  appear  oval  in  outline ;  and  then, 
elongating  more  and  more,  an  unmistakable  head  and  tail 
will  soon  appear.  At  length  the  embryo  becomes  active, 
and  breaks  through  the  jelly-like  mass,  and  is  hatched. 
It  attaches  itself  for  a  short  time,  by  means  of  a  pair  of 
minute  suckers  near  the  mouth,  to  the  jelly-like  mass  or 
to  plants,  but  soon  becomes  a  free-swimming  tadpole.  It 
then  breathes  by  means  of  three  pairs  of  external  gills, 
which  appear  as  minute  tufts  at  the  sides  of  the  head. 
The  water  passes  in  at  the  mouth,  and  out  through  three 
pairs  of  gill  slits  located  just  in  front  of  the  gills. 

If  one  of  these  small  tadpoles  be  placed  in  a  watch  glass 


THE   FROG.  197 

of  water,  and  examined  under  low  power  of  microscope, 
the  circulation  of  the  blood  may  be  beautifully  seen  in 
its  gills. 

As  the  tadpole  grows,  a  membranous  fold  (operculuni) 
arises  in  front  of  the  gills,  and  extends  backward  until  it 
covers  them.  On  the  right  side  of  the  body,  this  fold 
becomes  closely  adherent  by  its  posterior  margin,  thus 
closing  the  exit  of  the  water  on  that  side ;  but  a  trans- 
verse passage  is  developed  below,  so  that  all  the  water 
from  both  gill  chambers  passes  out  through  the  aperture 
remaining  on  the  left  side.  As  soon  as  the  external  gills 
are  covered,  they  begin  to  disappear  by  absorption  (atro- 
phy), and  internal  gills  are  developed  on  the  inner  side 
of  the  gill  slits.  Compare  the  structure  of  the  tadpole, 
at  this  stage,  with  that  of  the  fish. 

Later  a  pair  of  legs  appear  on  the  sides  of  the  base  of 
the  tail,  at  first  beneath  the  skin,  but  soon  becoming  free. 
Another  pair  is  developed  beneath  the  operculum,  and 
lungs  begin  to  be  developed  within  the  body  cavity. 
Then,  by  a  final  molting  of  the  skin,  the  opercular  mem- 
brane is  shed,  the  fore  legs  are  set  free,  and  the  eyes  are 
fully  exposed.  Finally  the  gills  are  absorbed,  and  lungs 
become  fully  developed,  and  aquatic  is  exchanged  for 
aerial  respiration.  The  gill  slits  close,  the  tail  is  ab- 
sorbed, and  the  tadpole  has  become  a  frog. 

This  brief  account  of  the  frog's  life  history  touches 
only  a  few  of  the  most  salient  points,  all  of  which,  and 
more  than  which,  the  careful  student  will  see  for  him- 
self. 

Each  student  should  dissect  a  large  tadpole,  and  should 
compare  the  internal  organs  with  those  of  an  adult  frog. 
Each  student  should  find  out  what  articles  constitute  the 
tadpole's  vegetable  diet,  and  should  note,  that,  with  the 
change  to  a  diet  of  animal  food  in  the  adult,  there  is  a 
great  decrease  in  the  relative  length  of  the  intestine. 


198  VERTEBRATES. 

Each  student  should  make  a  series  of  outline  drawings, 
illustrating  the  life  history  of  the  frog. 

The  frog  is  a  representative  of  the  group  Batrachia,  of 
which  tree  frogs,  toads,  newts,  efts,  and  salamanders  are 
also  members. 

THE  TURTLE. 

Haunts  and  Habits.  —  The  pond  turtles  or  mud  turtles 
(Pseudemys  and  Chrysemys),  so  abundant  in  our  small 
inland  lakes  and  sluggish  streams,  are  recommended  for 
study.  In  some  places  remote  from  water,  the  common 


MUD  TURTLE  (Chrysemys  picta). 

box  turtle  (Cistudo)  will  be  more  easily  obtainable.     It 
is  very  often  picked  up  in  dry  wood  or  fields. 

The  pond  turtles  are  very  shy,  and  somewhat  difficult 
to  secure  alive  by  ordinary  methods.  They  clamber  out 
of  the  water  upon  the  trunks  of  fallen  trees  along  the 
banks  of  secluded  ponds  and  streams,  and  lie  in  the  sun 
for  hours  at  a  time,  often  scores  of  them  together,  of 
all  ages  and  sizes ;  but  when  they  are  approached,  they 
tumble  precipitately  back  into  the  water,  and  disappear. 
They  may  be  bought  from  fishermen.  They  may  be 
dredged  or  raked  up  from  the  bottom  with  a  large  rake 
used  from  a  boat.  They  may  be  caught  with  hook  and 
line,  but  a  stout  line  will  be  necessary.  A  small,  compact 
piece  of  meat  should  be  used  for  bait.  A  supply  of  speci- 


THE   TURTLE.  199 

mens  should  be  obtained  while  the  weather  is  yet  warm 
in  autumn,  and  kept  until  needed.  They  may  be  kept 
alive  for  an  indefinite  length  of  time,  without  food,  dur- 
ing cold  weather.  In  the  winter  season  they  are  normally 
inactive,  and  if  kept  in  a  moist,  cool  place,  will  need  no 
looking  after. 

Study  of  a  Live  Specimen.  —  Study  the  turtle  alive. 
After  treating  it  to  a  good  washing  to  remove  the  mud, 
take  it  into  the  laboratory,  and  study  its  locomotion  :  — 

1.  Its  walking.     Note  the  position  of  its  legs  with  ref- 
erence to  the  body,  the  distance  between  its  lower  sur- 
face and  the  surface  on  which  it  walks,  its  rate  of  speed. 

2.  Its   swimming   and   diving.      Place   it   in   sufficient 
water,  and  observe  how  its  legs  are  used  in  these  acts. 

Is  its  form  well  adapted  for  rapid  locomotion  of  any  sort  ? 

Note  how  completely  its  head  and  appendages  may  be 
retracted  within  the  shell. 

Thrust  a  pencil  toward  the  eye,  and  observe  a  thin, 
transparent  membrane  come  out  from  the  inner  u  corner," 
where  it  lies  folded,  sweep  across  the  eyeball,  and  with- 
draw again.  This  is  the  third  eyelid  (or  nictitating  mem- 
brane). 

Respiration  takes  place  very  slowly,  but  occasionally  the 
animal  may  be  seen  to  swallow  a  mouthful  of  air. 

External  Features.  —  Note  among  the  external  features 
the  following:  — 

1.  The  relative  size  of  head  and  body. 

2.  The  hard  shell  or  case  which  nearly  incloses  the 
body.     It  consists  of  a  convex  dorsal  plate,  the  carapace, 
and  a  flat  ventral  plate,  the  plastron;  and  the  two  plates 
are  united  by  a  bony  bridge  at  either  side. 

3.  The  color  and  markings  of  the  wrinkled  skin  cover- 
ing the  neck  and  legs.     Is  any  part  of  it  scaly  ? 


200  VERTEBRATES. 

Kill  the  animal  with  chloroform.  The  best  way  to  do 
this  speedily  is  to  draw  the  head  forcibly  out  with  a 
tenaculum,  open  the  mouth,  find  the  opening  into  the 
trachea  at  the  base  of  the  tongue,  and  with  a  syringe  or 
a  large  pipette  inject  into  it,  and  through  it  into  the 
lungs,  a  teaspoonful  more  or  less  of  chloroform. 

When  the  muscles  are  relaxed,  draw  out  the  head, 
noting  the  length  of  the  neck  and  the  position  it  assumes 
when  retracted.  Note  the  horizontal  extension  of  the 
legs,  their  length,  and  range  of  movability.  Find  three 
principal  divisions  in  each,  as  in  the  frog.  Notice  in  the 
sides  of  the  body  the  "  pockets  "  into  which  the  retracted 
legs  fit. 

Examine  the  head.  Note  its  shape.  Note  the  relative 
size  and  position  of  nostrils,  eyes,  and  ears.  Note  the 
position  of  the  nictitating  membrane  of  the  eye ;  the  color 
of  the  iris. 

Open  the  mouth  and  examine  the  beak,  which  consists 
of  the  horny  sheaths  which  incase  the  edges  of  the  jaws. 
Observe  how  these  sheaths  fit  together  when  closed.  Find 
two  nostril  openings  into  the  roof  of  the  mouth  ;  openings 
of  two  Eustachian  tubes  on  the  sides,  back  of  the  muscles 
which  close  the  jaws  (not  easily  seen  from  the  front,  better 
seen  when  the  head  is  dissected)  ;  the  opening  into  the 
trachea,  on  the  floor  of  the  mouth,  and  the  esophagal 
opening  behind  it. 

Observe  that  the  horny  sheaths  of  the  jaws,  and  also 
the  scales  forming  the  external  layer  of  the  shell,  are  con- 
tinuous with  the  skin  of  the  body.  Both  are  thickened 
outgrowths  from  its  outer  (epidermal)  layer,  similar  in  kind 
to  the  smaller  scales  found  on  certain  parts  of  the  skin. 

Dissection.  — With  a  saw  or  chisel  cut  through  the 
bony  bridges  between  carapace  and  plastron.  Place  the 
turtle  on  its  back.  Cut  the  plastron  free  from  the  skin 


THE   TURTLE.  201 

all  around  the  border,  and  carefully  dissect  the  plastron 
free  from  all  its  attachments,  and  entirely  remove  it. 
See  the  points  where  it  was  connected  by  ligaments  with 
the  pectoral  and  pelvic  arches.  Muscles  already  severed 
from  their  origin  on  the  plastron  cover  the  bones  of  these 
arches.  Dissect  these  muscles  carefully  away,  noting 
that  they  are  opposed  in  pairs  on  each  half  of  each  arch. 
Find  nerves  and  blood  vessels  entering  them  internally. 
Avoid  cutting  any  large  branches  of  the  blood  vessels. 

The  peritoneum,  covering  the  posterior  part  of  the  body 
cavity,  should  still  be  intact,  and  on  its  inner  surface  a 
pair  of  abdominal  veins  should  be  plainly  seen. 

The  heart  should  be  seen  still  pulsating  in  its  thin 
pericardium,  in  the  anterior  part  of  the  body. 

The  abundant  transparent  liquid  which  fills  the  spaces 
within  pericardium  and  peritoneum  is  lymph. 

Placing  a  thumb  inside  each  half  of  the  pectoral  arch, 
press  outward  until  its  ligamentous  attachment  with  the 
inside  of  the  carapace  is  broken.  Then  draw  the  fore 
legs  forward  and  outward,  to  separate  the  halves  of  the 
pectoral  arch,  and  fasten  them  so. 

I.  The  Heart.  —  Open  the  pericardium,  and  fully  dis- 
close the  heart  and  its  connections.  Observe  :  — 

1.  A  single  large  posterior  ventricle. 

2.  A  pair  of  smaller  auricles. 

3.  White,  elastic  arteries  arising  from  the  ventricle. 

4.  Thinner-walled,  darker-colored   veins   entering   the 
auricles,  and  expanded,  just  before  they  enter,  to  form  a 
contractile  venous  sinus. 

Note  the  order  of  contraction, — first  the  venous  sinus, 
then  the  auricle,  then  the  ventricle.  This  wave  of  con- 
traction pushes  the  blood  forward,  and  indicates  the  direc- 
tion in  which  it  is  flowing  through  these  parts.  If  the 
blood  vessels  be  now  injected,  they  will  be  much  more 
easily  traced  later. 


202  VERTEBRATES, 

Divide  the  peritoneum  along  the  median  line,  and  dis- 
close the  internal  organs.1 

II.  Digestive   Organs.  —  Trace   the    digestive    system, 
finding  in  order  :  — 

1.  Esophagus. 

2.  Stomach. 

3.  Intestine  of  three  distinguishable  parts  :  — 

(a)  Duodenum,  into  which  ducts  from  the  gall  bladder 
of  the  liver  and  from  the  pancreas  open. 

(6)  Small  intestine. 

(<?)  Large  intestine ;  and  at  the  junction  of  these  two 
latter  parts,  a  short,  lateral,  hollow  process  (the  ccecum). 
The  spleen  lies  near  the  caecum. 

III.  Renal  and  Reproductive  Organs. — The   reproduc- 
tive  organs   cover   the   kidneys  and   often   other   parts. 
Find  a  pair  of  kidneys  communicating  posteriorly  with  a 
bilobed  urinary  bladder.     Make  a  diagrammatic  drawing 
of  all  these  parts.     Make  a  drawing  of  the  liver,  showing 
its  right  and  left  lobes  connected  with  a  transverse  band. 

IV.  Veins  and  Arteries.  —  Trace  the  two  anterior  ab- 
dominal veins,  seen  through  the  peritoneum,  before  open- 
ing the  body  cavity,  forward  to  the  liver.     Do  they  unite 
before  entering  the  liver  ?    Trace  veins  from  the  hindmost 
parts  of  the  body  to  the  kidneys,  thence  to  the  liver,  and 
thence  to  the  venous  sinus.     Find  veins  which  come  from 
anterior  parts  of  the  body,  also  entering  the  venous  sinus. 

Trace  now  the  principal  arteries.  Observe  that  the  two 
aortic  arches  and  the  pulmonary  artery  arise  separately 
from  the  ventricle,  and  not  from  an  arterial  trunk,  as  in 
the  frog.  Trace  the  pulmonary  artery  to  the  lung,  and 

1  After  dissecting  two  other  vertebrates,  the  fish  and  the  frog,  the 
student  should  not  now  need  further  specific  directions  for  finding  and 
studying  the  nutritive  and  reproductive  organs.  He  should  rather  let  his 
knowledge  of  the  structure  of  those  vertebrates  serve  as  a  guide  to  the 
study  of  this  one ,  and  he  should  not  fail  diligently  to  compare  this  one 
with  the  other  two  at  every  point. 


THE   TURTLE.  203 

the  pulmonary  vein  back  to  the  heart.  Trace  branches 
of  the  aortie  anteriorly  to  the  head.  Trace  the  aortae 
themselves  posteriorly,  to  see  their  union  and  subsequent 
division,  and  distribution  to  the  various  parts.  Now 
make  a  diagram  showing  the  general  arrangement  of  the 
circulatory  system. 

V.  Retractor  and  Protractor  Muscles.  —  Study  the  action 
of  the  long  retractor  muscles  which  extend  from  the  middle 
of  the  spinal  column  to  the  base  of  the  skull,  and  of  the 
protractor  muscles,  which  extend  from  carapace  and  pec- 
toral arch  to  the  neck.     Pull  first  on  one  and  then  on  the 
other,  and  note  the  effect  on  the  head  and  neck. 

VI.  Trachea  and  Lungs. — Extend  the  neck,  and  fasten 
it  so.     Dissect  out  the  trachea  and  the  lungs.     Inflate  the 
lungs,  and  keep  them  inflated  by  tying  the  trachea  with  a 
thread.     Hang  them  up,  and  let  them  dry,  and  preserve 
them  for  comparison  with  the  lungs  of  other  vertebrates. 

The  narrow  slit  by  which  the  trachea  opens  on  the 
floor  of  the  mouth  is  the  glottis.  Why  does  not  food 
which  is  being  swallowed  get  into  the  trachea? 

VII.  Spinal  and  Cranial  Nerves  and  Brain.  —  Remove 
the  viscera,  and  find  spinal  nerves.     Compare  in  number 
and  arrangement  with  those  of  the  frog.     Remove  the  roof 
of  the  cranium,  and  find  cranial  nerves  and  brain.     In  the 
brain  find  in  order  from  the  front,   (1)  olfactory  lobes, 
(2)  cerebral  hemispheres,  (3)  midbrain,  (4)  optic  lobes, 
(5)  cerebellum,  and  (6)  medulla. 

Study  of  the  Skeleton.  —  Study  the  shell  of  the  turtle, 
especially  in  its  relation  to  the  bony  skeleton.  In  a 
prepared  skeleton  of  an  adult  turtle,  note  :  — 

1.  That  the  pectoral  and  pelvic  arches,  and  the  bases 
of  the  legs,  are  contained  within  the  shell. 

2.  That  both  arches  are  attached  more  or  less  closely 
at  several  points  to  both  carapace  and  plastron. 


204  VERTEBRATES. 

3.  That  the  spinal  column  is  coossified  with  the  cara- 
pace, only  the  vertebrae  of  neck  and  tail  remaining  free 
and  movable. 

I.  The  Shell :  Exoskeletal  Parts.  —  Examine  the  plas- 
tron. On  its  ventral  surface  find  six  pairs  of  flat,  horny 
plates,  with  two  additional  smaller  pairs,  forming  the 
margins  of  the  bridges  meeting  the  carapace.  On  its 
dorsal  or  inner  surface  find  four  pairs  of  plates  and  one 
single  plate  of  bone.  Note  that  the  boundaries  of  the 
horny  plates  on  the  ventral  surface  do  not  correspond 
to  the  boundaries  of  the  bony  plates  on  the  dorsal  sur- 
face. The  horny  plates,  like  the  scales  of  other  parts, 
are  developed  from  the  outer,  epidermal  layer  of  the  skin, 
and  are  therefore  called  epidermal  plates.  The  bony 
plates  are  developed  from  the  deeper  layer  of  the  skin 
(dermis),  and  are  called  dermal  plates. 

Examine  the  carapace.  Its  convex  surface  is  com- 
pletely covered  over  with  epidermal  plates,  as  follows :  — 

On  the  median  line,  at  the  anterior  edge,  is  a  small, 
single  nuchal  plate  (sometimes  a  pair  of  nuchal  plates). 

Posterior  to  this,  on  the  median  line,  are  five  large 
central  plates. 

A  pair  of  pygal  plates  meet  on  the  median  line,  at  the 
posterior  edge. 

The  central  plates  are  bordered  laterally  by  four  pairs 
of  large  centrolateral  plates. 

The  margins  of  the  shell  between  the  nuchal  and  pygal 
plates  are  formed  by  eleven  pairs  of  marginal  plates. 

Dermal  plates  are  developed  beneath  the  marginal 
nuchal  and  pygal  epidermal  plates,  and  correspond  with 
them  in  position,  in  names,  and  in  number,  save  that  the 
nuchal  and  pygal  plates  are  single. 

The  dermal  and  epidermal  plates  together  constitute 
the  outside  skeleton  or  exoskeleton,  as  distinguished  from 
the  true  internal  skeleton  (or  endoskeleton). 


THE   TURTLE.  205 

The  relation  between  the  plates  which  make  up  the 
shell  can  be  better  understood  by  separating  them.  If 
the  specimen  which  was  used  for  dissection,  after  being 
freed  from  most  of  its  soft  parts,  be  dipped  into  boiling 
water  for  a  few  minutes,  the  horny  epidermal  (tortoise- 
shell)  plates  may  be  readily  stripped  off.  If  then  it  be 
boiled  thoroughly,  the  marginal  nuchal  and  pygal  dermal 
plates  may  be  removed.  There  will  then  remain  only  the 
endoskeleton,  forming  still  a  considerable  part  of  the  con- 
cave surface  of  the  carapace. 

II.  Endoskeletal  Parts.  —  On  the  convex  surface,  as  it 
is  now  exposed,  there  will  be  seen  markings  correspond- 
ing to  the  edges  of  the  epidermal  plates  which  have  been 
stripped  off.     Observe  that  these  markings  do  not  at  all 
correspond  to  the  outlines   of    the  plates  of   bone    they 
overlie.     These  plates  of  bone  are  arranged  in  longitudi- 
nal series  as  follows  :  — 

There  is  a  central  row  of  eight  plates  formed  by  the 
lateral  expansion  of  the  neural  spines  of  eight  of  the  ver- 
tebrae, and  hence  called  neural  plates. 

There  are  two  lateral  rows,  each  of  eight  plates,  formed 
by  the  expansion  of  eight  pairs  of  ribs,  and  hence  called 
costal  plates. 

III.  The  Spinal  Column.  —  Study  now  the  arrangement 
of   bones,  as  seen  on   the  concave  side  of   the  carapace. 
The  spinal  column  marks  the  median  line.     In  it  are  four 
distinguishable  regions : — 

1.  A  cervical  region,  extending  from  the  head  to  the 
shoulder  girdle.     The  cervical  vertebrae  bear  no  ribs,  and 
are  not  attached  directly  to  the  carapace. 

2.  A  dorsal  region,  of  rib-bearing  vertebrae,  cob'ssified 
with  the  carapace. 

3.  A  sacral  region,  of  two  vertebrae,  not  attached  directly 
to  the  carapace,  bearing  ribs  which  unite  distally  to  form 
a  facet  for  articulation  with  a  bone  of  the  pelvic  arch. 


206  VERTEBRATES. 

4.  A  terminal  caudal  region,  of  many  small  vertebrae, 
without  developed  ribs,  tapering  posteriorly  to  the  tip. 

The  dorsal  vertebrae  are  the  ones  concerned  in  the 
formation  of  the  carapace.  Observe  that,  of  the  ten  dorsal 
vertebrae,  each  one,  except  the  first  and  the  last,  bears  a 
neural  plate  and  a  pair  of  costal  plates.  Observe  that 
the  ribs  from  the  first  dorsal  attach  to  the  costal  plates  of 
the  second,  and  that  the  ribs  from  the  tenth  attach  to  the 
costal  plates  of  the  ninth.  Notice  that  several  of  the 
anterior  pairs  of  ribs  appear  to  have  moved  forward  until 
they  articulate  with  the  centra  of  two  vertebrae.  Notice 
the  finely  toothed  sutures  by  which  the  costal  plates  meet 
each  other. 

How  many  of  the  points  noted  in  the  structure  of  the 
shell  are  directly  conducive  to  its  strength? 

How  many  caudal  vertebrae  are  there?  How  many 
cervical?  Observe  that  the  first  cervical  meets  the  skull 
by  a  single  occipital  condyle.  Separate  the  cervical  ver- 
tebrae, and  note  the  great  variety  of  articulating  surfaces 
between  the  ends  of  adjacent  centra. 

IV.  Girdles  and  Leg  Bones.  —  In  each  half  of  the 
shoulder  girdle  there  are  three  bones  :  — 

1.  The  bone  which  extends  from  the  shoulder  dorsally, 
to  meet  the  first  costal  plate,  is  the  scapula. 

2.  The  posterior  of  the  two  bones  which  extend  from 
the  shoulder  toward  the  median  line  is  the  coracoid.     It 
is  horizontally  flattened  toward  its  inner  end,  there  be- 
coming somewhat  triangular. 

3.  The  anterior  of   the   horizontal   bones   is  the  pre- 
coracoid. 

In  each  half  of  the  pelvic  girdle  there  are  three 
bones :  — 

1.  The  bone  which  extends  from  the  acetabulum  dor- 
sally, to  meet  the  sacral  ribs,  is  the  ilium. 

2.  The  posterior  of  the  two  bones  which  extend  from 


THE   TURTLE.  207 

the  acetabulum  horizontally,  toward  the  median  line,  is 
the  ischium. 

8.    The  anterior  of  the  two  horizontal  bones  is  the  pubis. 

Between  ischium  and  pubis  is  a  large  hole,  the  obturator 
foramen.  Ischia  and  pubes  of  opposite  sides  meet  in  a 
median  ventral  symphysis. 

In  both  fore  and  hind  legs  find  the  parts  already  found 
in  the  legs  of  the  frog,  observing  the  separation  of  the 
two  bones  of  the  forearm  and  the  two  of  the  shank,  and 
the  shortness  of  the  tar  sal  bones. 

Development.  — The  eggs  of  certain  species  of  turtles 
(the  eggs  which  are  perhaps  most  easily  found)  are  laid 
in  early  summer  in  sunny  sandbars  in  rivers,  lakes,  and 
creeks.  At  night  the  mother '  turtle  digs  down  into  the 
sand,  and  hides  away  her  eggs  a  foot  or  more  beneath  the 
surface,  smooths  the  sand  above  them,  and  leaves  them 
to  be  hatched  by  the  warmth  of  the  sand,  absorbed  from 
the  sun's  rays.  Although  the  mother  turtle  has  been 
careful  to  remove  visible  traces  of  their  whereabouts,  they 
may  yet  be  found  by  very  simple  means.  The  disturbed 
sand  in  which  they  lie  is  much  more  readily  penetrated  by 
a  stick  than  are  other  places  on  the  bar.  Hence,  if  a  stick 
be  pushed  into  the  sand  at  short  intervals  along  the  line 
of  the  turtle's  tracks,  and  a  place  be  found  where  it  enters 
very  much  more  readily  than  elsewhere,  that  is  the  place 
to  look  for  the  "nest."  The  unmistakable  tracks  of  the 
turtle  across  sunny  bars  of  pure  sand  will  seldom  be  fol- 
lowed in  vain  in  May  or  June  ;  for  the  turtles  do  not 
ordinarily  frequent  such  places. 

The  young  turtle  which  hatches  from  the  egg  is  essen- 
tially like  the  adult,  except  in  size.  It  differs  somewhat 
in  having  its  legs  and  pectoral  and  pelvic  arches  free  from 
the  shell.  During  later  development  the  sHell  encroaches 
upon,  and  partially  incloses,  these  parts.  Young  in  all 


208  VERTEBRATES. 

stages  may  be  captured  in  the  same  situations  with  the 
adults. 

No  good  conception  of  the  life  this  animal  leads  can  be 
obtained  in  the  laboratory.  After  studying  it  there,  the 
student  should  spend  a  day  or  two  early  in  his  summer 
vacation  studying  the  animal  in  its  native  haunts,  learning 
of  its  curious  habits,  and  of  the  peculiar  place  it  fills  in 
the  economy  and  society  of  nature. 

The  turtle  is  a  representative  of  the  class  Reptilia  (or 
reptiles). 

Other  Reptilia.  —  Lizards,  snakes,  and  alligators  also 
belong  to  the  Reptilia. 

THE  SNAKE. 

Lizards  and  Snakes  present  types  of  reptilian  structure 
so  markedly  different  from  that  seen  in  the  turtle  that 
the  following  outline  is  subjoined  to  enable  the  student  to 
know  how  to  proceed  in  case  a  study  of  either  of  these 
forms  is  to  be  undertaken.  For  guidance  in  studying 
the  details  of  their  structure,  he  is  referred  to  the  refer- 
ence works  mentioned  elsewhere.  This  meager  outline  is 
written  for  the  snake,  but  may  be  applied  without  much 
change  to  the  study  of  any  common  lizard. 

Study  of  the  Live  Specimen.  —  Get  a  garter  snake 
(Eutania),  or  a  black  snake  (Bascaniori),  or  any  other 
common  harmless  species,  and  study  it  alive.  Notice  the 
exceeding  gracefulness  of  its  movements,  the  slenderness 
of  its  flexuous  form,  the  ease  of  its  gliding  motion,  and 
the  beauty  and  harmony  of  its  coloration.  Observe  :  — 

1.  The  entire  absence  of  limbs.      How  is  its  rapid  pro- 
gression effected  ? 

2.  The  position  it  assumes  when  molested  and  brought 
to  bay,  and  its  method  of  defense. 


THE  SNAKE.  209 

3.  Protective  resemblance;  i.e.,  likeness  in  form  and 
coloration  to  the  natural  objects  by  which  it  is  surrounded 
when  in  its  native  haunts.  Considering  that  the  snake  is 
a  predacious  animal,  what  are  the  advantages,  both  pro- 
tective and  offensive,  of  being  inconspicuous  ? 

External  Features.  —  Place  the  snake  and  a  small  pieco 
of  sponge  or  bunch  of  cotton  saturated  with  chloroform 
in  a  tight  box  or  under  a  bell  jar,  and  as  soon  as  the  snake 
is  dead  extend  it  lengthwise  on  the  table  and  note  its 
external  features.  Observe  :  — 

1.  The  general  form  of  the  body. 

2.  The  more  or  less  distinct  head. 

3.  The  long  tapering  tail. 

4.  The  complete  covering  of  scales. 

5.  The  relation  of  the  scales  to  each  other  and  to  the 
underlying  skin.     . 

6.  The  form  of  the  scales  — 

(a)  On  the  head. 

(b)  On  the  back  and  sides. 

(c)  On  the  ventral  surface  of  both  body  and  tail.     The 
wide  ventral  plate-like  scales  on  which  the  body  rests  are 
the  gastrosteges.     The  hindmost  of  the  gastrosteges  is  the 
anal  plate.     Observe  whether  it  is  entire  or  bifid.     The 
paired  plates  beneath  the  tail  are  the  urosteges. 

Search  the  eye  for  eyelids ;  the  sides  of  the  head  for 
ears  ;  the  front  of  the  head  for  nostrils. 

Dissection.  —  Stretch  the  snake  back  downward  upon  a 
board,  and  fasten  it  so  with  a  tack  through  the  tail  and 
two  others  through  the  edges  of  the  upper  jaw.  Leave 
the  lower  jaw  free.  With  forceps  pull  this  upward  and 
sidewise,  and  note  how  loosely  its  halves  (rami)  are 
united  at  their  tips.  Note  :  — 

1.  The  looseness  of  the  hinge  by  which  the  lower  jaw 
is  attached  to  the  cranium. 

NEED.  ZOOL.  —  14 


210  VERTEBRATES. 

2.  The  dilatability  of  the  mouth  and  throat. 

3.  The  position,  shape,  and  direction  of  the  teeth.    Are 
they  adapted  for  chewing  food  ?     In  what  condition  does 
the  snake  swallow  its  prey  ? 

With  forceps  draw  the  forked  tongue  from  its  sheath, 
and  note  its  character  and  length. 

Find  behind  the  tongue  a  small  opening  into  the  trachea, 
the  glottis,  and  behind  the  glottis  the  opening  into  the 
esophagus. 

With  sharp  scissors  split  the  abdominal  wall  down  the 
median  ventral  line  to  the  tail.  Fasten  the  cut  edges 
wide  apart  with  tacks. 

Internal  Features.  —  Without  further  dissection  make 
out  the  following  parts:  — 

1.  The  heart  lies  in  the  central  anterior  portion  of  the 
body,  inclosed  within  its  thin  transparent  pericardial  sac. 
The  large  conic  posterior  portion  is  the  ventricle.     The 
two  lobes  beside  its  anterior  end  are  the  auricles. 

2.  The  brownish  elongated  organ  lying  along  the  left 
side  of  the  body  is  the  liver. 

3.  Beneath  the  liver  is  the  stomach.     Leading  from  the 
mouth  to  the  stomach  is  the  esophagus,  and  posterior  to 
the  stomach  is  the  intestine. 

4.  Posterior  to  the  liver,  and  lying  close  to  the  begin- 
ning of  the  intestine,  is  the  dark  gall  bladder.     Close  be- 
side it  is  the  spherical  spleen. 

F.  Posterior  to  these  are  the  elongated,  light-colored 
kidneys,  one  on  either  side,  communicating  with  the 
exterior  by  a  very  long  and  much  crimped  duct. 

6.  Posterior  to  all  these  are  the  paired  reproductive 
organs,  each  with  a  separate  straight  duct  lying  alongside 
that  of  the  kidney. 

Lungs  and  Blood  Vessels.  —  From  the  glottis  the  ringed 
trachea  may  be  traced  back  to  the  pink  lung,  which  lies  on 


THE  ENGLISH  SPARROW.  211 

the  right  side  of  the  body.  Insert  a  blowpipe  into  the 
glottis  and  inflate  the  lung.  Observe  a  prominent  branch- 
ing pulmonary  artery  running  along  the  inner  side  of  the 
lung.  Cut  away  the  upper  part  of  the  pericardium  and 
trace  this  artery  back  to  the  heart.  Through  it  blood  is 
conveyed  from  the  heart  into  the  lung  for  aeration. 

Observe  on  the  inner  side  of  the  liver  a  prominent  vein 
coming  from  the  posterior  part  of  the  body  cavity,  bring- 
ing the  blood  back  to  the  heart.  Trace  outward  from 
the  heart  the  aorta  (the  principal  artery),  which  arises 
from  the  ventricle  between  the  auricles,  bends  upward  and 
backward  about  the  esophagus,  and  passes  straight  through 
the  body  cavity  posteriorly,  giving  off  branches  which 
supply  blood  to  all  the  parts. 

The  lung  is  single,  but  the  rudiment  of  its  undeveloped 
mate  may  be  found  by  dissecting  out  the  trachea.  Dis- 
sect out  the  lung.  Inflate  it  through  the  glottis,  and  tie 
the  trachea  with  a  thread  to  keep  it  inflated.  Dry  it,  and 
compare  it  in  structure  with  the  lungs  of  the  frog  and  the 
turtle. 

Compare  the  snake  with  the  turtle  in  respect  to  — 

1.  Means  of  locomotion. 

2.  Character  of  mouth  parts. 

3.  Character  of  scales. 

4.  Shape  of  body  cavity. 

5.  Relative  development  of  internal  organs. 


THE  ENGLISH  SPARROW. 

(Passer  domesticus.) 

An  Interloper.  —  This  bird  and  its  haunts  are  too  well 
known  to  need  description.  It  was  introduced  into  the 
United  States  about  1850,  and  has  since  overspread  the 
whole  country.  It  is  the  only  bird  to  be  found  in  many  of 


212  VERTEBRATES. 

our  cities  and  towns.  Because  it  is  surely  supplanting 
our  more  desirable  native  birds,  the  student  is  recom- 
mended to  find  a  scientific  use  for  as  many  specimens  as 
possible. 

Collecting,  —  There  are  many  ways  of  obtaining  live 
specimens.  A  few  are  suggested  :  the  ingenious  student 
will  devise  other,  and  perhaps  better,  means.  A  trap, 
consisting  of  a  common  wooden  box,  set  with  a  figure-4 
trigger,  and  baited  with  any  kind  of  grain  or  with  a 
crust  of  bread,  will  usually  obtain  specimens,  but  not 


Female.  Male. 

ENGLISH  SPARROW  (Passer  domesticus). 

oftener  -than  once  in  one  place.  Sparrows  often  roost 
in  sheds  and  outbuildings,  which  may  be  closed  after 
dark,  and  all  the  inmates  secured.  When  found  roost- 
ing in  a  vine  or  shrubbery,  they  may  often  be  sur- 
rounded with  a  large  sheet,  and  captured  within  it. 

Field  Study.  —  Study  the  bird  in  its  relation  to  nature. 
On  the  street  and  on  the  lawn  observe,  as  opportunity 
daily  offers,  the  habits  of  the  bird,  until  you  are  able  to 
answer  the  following  and  related  questions :  — 

1.  Is  the  sparrow  solitary,  or  sociable,  in  its  habits  ? 

2.  What  kind  of  a  voice  has  it  ?     Can  it  properly  be 
said  to  sing  ?     Has  it  different  notes  for  different  occa- 
sions, and  can  you  discover  what  any  of  its  notes  mean  ? 


THE   ENGLISH   SPARROW.  213 

3.  Can  it  hear  well  ? 

4.  Is  its  sight  as  keen  as  your  own  ? 

5.  What  does  it  eat  ?      It  was  imported   in  the  hope 
that  it   would   rid   the  country  of   certain   insect  pests. 
Do  you  find  it  eating  insects  at  all? 

6.  If  other  species  of   birds   are  found    in   the   same 
locality,  how  do  the  sparrows  behave  toward   the  other 
birds  ? 

7.  What  kind  of  a  nest  does  the  sparrow  build  ?     At 
what  season  ?    Out  of  what  materials  ?    How  put  together  ? 
Where  is  it  located  ? 

8.  How  many  eggs  are  laid  in  the  nest  ?     How  long  are 
these  in  hatching  ?     How  long  before  the  little  birds  leave 
the  nest  ?     What  do  the  fledgelings  eat  ?     How  do  they 
get  their  food  ?     Is  more  than  one  brood  reared  each  sum- 
mer by  a  single  pair  ? 

9.  What  physical  casualties  of  weather,  temperature, 
etc.,  have  you  observed  to  destroy  the  eggs  or  young? 

10.  What  are  the  natural  enemies  of  the  species  ? 

11.  Are  the  fatalities  to  the  young  more,  or  less,  fre- 
quent than  with  other  animals  you  have  studied? 

Study  of  a  Live  Specimen. — With  a  live  bird  in  hand, 
note : — 

1.  The  shape  of  its  body.     How  is  ifc  adapted  for  pro- 
gression through  the  air  ?     How  does  the  plumage  of  the 
body  improve  this  adaptation  ? 

2.  The  shape  and  attachment  of  its  wings.     What  is 
their  shape  above  ?     Below  ?     What  is  their  anterior  out- 
line when  extended  ?     Their  posterior  ?     Find  three  prin- 
cipal joints  in  one  wing.     Note  the  zigzag  position  these 
joints  take,  even  in  the  extended  wing.     Note  the  mem- 
brane stretched  between  the  first  and  second  joints.     Of 
what  advantage  is   it  for  flying?     Why  are  the  wings 
attached  at  the  dorsal  side  of  the  body  ? 


214  VERTEBRATES. 

3.  The  action  of  the  wings.     How,  in  relation  to  the 
air,  are  they  moved  forward  ?    Backward  ?     How  are  they 
folded  up  ? 

4.  The  use  of  the  tail.    Permit  the  sparrow  to  fly  about 
a  closed  room,  and  observe  the  rudder-like  action  of  the 
tail.     When   the  tail  is  inclined  upward,  downward,  to 
right  or  to  left,  what  is  the  corresponding  direction  taken 
in  flight  ?     How  is   the  tail  used   in   effecting  a   quick 
stop? 

5.  The  shape  and  position  of  the  legs.     Note  the  zigzag 
position  of  the  three  principal  joints.     Note  the  position 
in  standing,  in  perching,  and  in  flight.     Placing  the  feet 
in  the  perching  position  on  one  finger,  note  how  the  toes 
automatically  close  and  open  when  the  body  is  lowered 
toward  the  finger,  or  raised  away  from  it. 

6.  The  action  of  the  legs.     Does  the  sparrow  walk  ? 
Slip  a  wide  rubber  band  over  the  wings  to  hold  them 
close,  or,  what  will  answer  the  same  purpose,  tie  their  tips 
together,  and  note  how  the  bird  gets  about  when  using  its 
legs  alone. 

7.  Respiration.     Note  what  parts  of  the  body  visibly 
expand  and  contract  in  breathing. 

8.  The  eyes.     What   position  do  the  eyelids   assume 
when  wide  open;    i.e.,  are  there  any  "corners"  to  the 
sparrow's  eye  ?     Thrust  a  pencil  toward  the  eye,  and  see 
the  nictitating  membrane  dart  out  across  the  eyeball,  and 
as  quickly  retreat  again.     Observe  the  round,  black  pupil 
in  the  center  of  the  front  of  the  eyeball,  and  the  circular 
brown  iris  surrounding  it.     Take  the  bird   into  a  dark 
place,  and  watch  the  pupil  enlarge.    Then  bring  it  quickly 
out  into  the  strong  light  again,  and  see  it  grow  smaller. 

Wet  a  small  piece  of  cotton  with  chloroform,  and  hold 
it  on  the  nostrils  of  the  bird  a  moment,  until  it  begins  to 
doze.  Then  tie  the  cotton  in  place,  add  a  few  more  drops 
of  chloroform,  and  lay  the  bird  down.  In  a  few  moments 


THE   ENGLISH   SPARROW.  215 

it  will  be  quite  dead,  and,  killed  in  this  way,  it  will  be 
in  excellent  condition  for  a  detailed  examination  of  its 
structure* 

Naming  of  External  Parts.  —  For  purposes  of  descrip- 
tion, the  external  parts  of  the  bird  are  named  as  follows  :  — 

I.  The  Head  and  Neck.  —  At  the  front  of  the  head  is 
the  beak,  "composed  of  upper  and  lower  mandibles.     The 
line  of  meeting  of  the  two  mandibles  is  the  commissure. 
Observe    that    in    the    sparrow    the    commissure    is    not 
straight,  but  angulated;  i.e.,  bent  downward  posteriorly, 
as  if  the  corners  of  the  mouth  were  drawn  downward. 
The  corner  of  the  mouth  is  called  the  rictus,  and  the 
bristles  overhanging  the  rictus  are  called  rictal   bristles. 
The  ridge  of  the  upper  mandible  is  called  the  culmen;  and 
the  keel  of  the  lower'  mandible,  the  gonys.     At  the  base 
of  the  upper  mandible  are  the  nostrils.     The  front  part 
of   the  top  of  the  head  is  the  forehead,  the  top  part  is 
the  crown,  the  back  part  is  the  occiput,  and  the  back  of  the 
neck  is  the  nape.     The  space  between   the  eye  and  the 
rictus  is  the  lore.     Below  and  behind  the  eye,  hidden  by 
a  tuft  of  loose  feathers,  is  the  ear.     Lift  up  these  feathers 
and  find  the  auditory  opening.     Examine  one  of   these 
feathers  with  a  lens.     What  advantage  is  there  in  having 
these  feathers  less  compact  than  the  others?     The  front 
part  of  the  under  surface  of  the  head  is  the  chin.     The 
front  of  the  neck  is  the  throat. 

Make  an  enlarged   outline   drawing  of   the   head   and 
neck,  naming  all  the  parts  upon  the  drawing. 

II.  The  Body  and  Tail.  — The  dorsal  surface  of  the  body 
is  the  back.     The  tufts  of  feathers  covering  the  bases  of  the 
wings  dorsally  are  the    scapulars.     The   prominent   nar- 
rowed  portion  of   the   back  immediately  preceding   the 
tail  is  called  the  rump.     The  long,  soft  feathers  that  over- 
lap the  tail  above  are  the  upper  tail  coverts.     The  long, 


216 


VERTEBRATES. 


stiff  feathers  of  the  tail  are  the  rectrices  (or  tail  feathers), 
oftenest  called  simply  the  tail  in  descriptions,  though 
they  are  only  a  part  of  the  exoskeleton  of  the  tail.  Be- 
neath the  rectrices  are  the  long,  soft  under  tail  coverts. 
The  small  area  of  loose  feathers  just  in  front  of  the  lower 
tail  coverts  is  the  crissum.  The  posterior  part  of  the 
remaining  lower  surface  is  called  the  abdomen  (or  belly)  ; 
and  the  anterior,  more  convex  part,  the  breast. 


pr  cov 


DIAGRAM  OF  SPARROW:  cul,  culmen;  I,  lore;  /,  forehead;  ee,  eye;  c,  crown; 
ea,  ear;  oc,  occiput;  n,  nape;  bk,  back;  r,  rump;  utc,  upper  tail  coverts; 
t,  tail;  Itc,  lower  tail  coverts;  crsm,  crissum;  6,  belly;  gon,  gonys; 
ch,  chin;  th,  throat;  br,  breast;  bnd,  bend  of  the  wing;  sc,  scapulars; 
pr,  primaries ;  sec,  secondaries ;  pr  cov,  primary  coverts ;  sec  cov,  secondary 
coverts;  sp,  spurious  quills;  tb,  tibia;  trs,  tarsus;  ft,  foot;  1,  2,  3,  and  4, 


III.  The  Wings.  - —  In  a  wing  find  parts  corresponding 
to  arm,  forearm,  and  hand.  The  long  feathers  which 
grow  on  the  most  distal  division,  or  hand,  are  the 
primaries.  Those  which  grow  on  the  middle  division  are 
secondaries.  In  some  birds,  but  not  in  the  sparrow,  there 
are  similar  feathers  growing  on  the  proximal  division, 
called  tertiaries.  The  short,  soft  feathers  which  overlap 
the  bases  of  the  primaries  and  secondaries  above  and  be- 
low are  called  upper  or  lower,  primary  or  secondary  coverts. 
At  the  bend  of  the  wing,  and  overlapping  the  upper  pri- 
mary coverts,  is  a  tuft  of  short  quills  (the  spurious 


THE   ENGLISH   SPARROW. 


217 


quills)  growing  upon  the  part  of  the  hand  which  corre- 
sponds to  the  thumb.  In  the  hollow  beneath  the  wing, 
at  its  junction  with  the  body,  is  a  tuft  of  long,  loose,  soft 
feathers  (the  axillars). 

Expand  the  wing,  and  arrange  all  the  feathers  naturally. 
Note  the  shape  and  curvature  of  the  primaries  and  sec- 
ondaries. Note  their  direction  of  overlapping.  Find  on 
the  wing  a  series  of  feathers  which  shingle  in  the  oppo- 
site direction.  Observe  the  position  of  the  coverts.  See 
how  beautifully  each  feather  falls  into  its  proper  place 
when  the  wing  is  closed,  how  compactly  the  whole  wing  is 
nestled  against  the  sides  of  the  body,  and  how  it  is  over- 
lapped by  the  other  plumage,  and  made  to  contribute  to 
the  symmetry  of  the  bird. 

IV.  The  Legs. —In.  a 
leg,  find  thigh,  shank,  and 
foot.  The  foot  consists  of 
a  long,  slender  tarsus,  and 
four  toes  terminated  by 
horny  claws.  The  tarsus 
is  made  up  of  several  tar- 
sal  bones  solidly  grown  to- 
gether (anchylosecT).  Note 
the  directions  the  toes  take, 
and  the  number  of  joints 
in  each.  What  parts  of  the 
leg  are  feathered  ?  What 
parts  covered  by  scales  ? 
What  kind  of  a  covering 
has  the  lower  surface  of 
the  foot  ? 


LEFT  LEG  OF  SPARROW  (from  inner 
side,  slightly  reduced) :  fe,  femur ; 
fi,  fibula;  t,  tibia;  trs,  tarsus  or 
tarsometatarsus ;  ra,  an  incomplete 
extra  metatarsal  at  base  of  hind  toe ; 
1,  2,  3,  4,  toes. 


Exoskeletal  Modifications.  —  In  this  external  examina- 
tion of  the  bird,  three  modifications  of  exoskeleton  will 
have  been  noticed. 


218  VERTEBRATES. 

1.  Horny  sheaths  covering  the  mandibles  and  claws. 

2.  Epidermal  scales  (^scutellce)  covering  the  tarsus  and 
toes. 

3.  Feathers   covering  the   remaining  exposed   portions 
of  the  skin,  and  constituting  the  plumage. 

But  there  are  hidden  areas  of  the  skin  which  are  bare. 
By  separating  the  feathers,  find  one  of  these  on  the  median 
line  of  the  breast,  and  another  on  either  side  of  the  base 
of  the  neck. 

Examine  the  stout,  thick  beak.  Such  a  beak  "is  well 
adapted  to  eating  grain,  —  to  breaking  the  husks  and 
hulling  out  seeds.  Examine  the  claws.  Are  they  sharp 
enough  to  be  of  much  service  as  defensive  weapons  ?  Are 
the  feet  strong  enough  to  indicate  that  the  claws  are  used 
for  defense  ? 

Examine  the  scales  of  the  tarsus  and  toes.  Note  that 
they  overlap  regularly  down  the  front  and  sides,  and  that 
a  posterior  series  forms  a  sharp  ridge  down  the  back  of  the 
tarsus.  A  tarsus  with  regularly  overlapping  scales  such 
as  these  is  said  to  be  scutellate. 

Plumage.  —  Examine  the  plumage.  Pluck  one  of  the 
longest  primaries  from  a  wing,  and  examine  it.  Observe 
a  median  shaft  bordered  on  either  side  by  a  web  (or  vane). 
Observe  that  the  shaft  is  made  up  of  two  parts,  —  a  lower 
transparent  part,  the  quill  (or  calamus)  ;  and  the  opaque 
part,  the  rhachis,  which  bears  the  vanes.  Make  a  cross 
section  through  the  calamus,  and  another  through  the 
rhachis.  What  is  the  shape  in  cross  section  of  the 
calamus  ?  Of  the  rhachis  ?  What  is  the  condition  of 
the  interior  of  the  calamus  ?  Of  the  rhachis  ?  Hold- 
ing the  rhachis  horizontally,  look  at  the  cut  end.  Com- 
pare the  position  of  the  vanes  in  relation  to  the  rhachis 
with  that  of  the  wings  of  the  bird  in  relation  to  the  body. 
Why  should  the  vanes  be  attached  to  its  upper  side  ? 


THE   ENGLISH   SPARROW.  219 

Observe  a  longitudinal  groove  on  the  under  side  of  the 
rhachis.  Place  a  needle  point  in  this  groove,  and  push 
it  along  toward  the  calamus  until  it  enters  a  small  hole 
(umbilicus).  Trace  the  vanes  downward  to  their  origin. 
Where  is  there  another  hole  leading  to  the  interior  of  the 
calamus  ? 

Examine  the  vane  with  a  lens.  The  thin,  narrow  linear 
plates  of  which  it  is  made  up  are  called  barbs.  Observe 
that  each  barb  is  fringed  with  similar  smaller  plates,  called 
barbules,  which,  by  their  interlacing,  form  a  true  web,  ana 
give  capacity  for  much  resistance  to  very  weak  filaments. 
If  a  piece  of  the  vane  be  soaked  for  a  time  in  strong  alco- 
hol, to  remove  air,  a  microscopic  examination  of  its  bar- 
bules will  discover  little  hooks  (hamuli)  along  a  portion  of 
their  margins. 

Pluck  one  of  the  small  rictal  bristles  from  just  above 
the  corner  of  the  mouth.  Examine  it  with  lowest  power 
of  microscope,  to  make  out  calamus,  rhachis,  and  partial 
vanes. 

There  is  one  other  part  present  in  many  feathers.  It 
may  be  found  in  one  of  the  surface  feathers  of  the  breast 
or  back.  Examine  one  of  these  with  a  lens.  Make  out 
calamus,  rhachis,  and  vanes,  and  find  in  addition  an  after- 
shaft  arising  from  the  summit  of  the  calamus,  behind  the 
rhachis.  Compare  the  aftershaft  with  the  parts  already 
studied. 

The  three  feathers  examined,  together  with  nearly  all 
others  that  are  exposed  on  the  surface,  and  that  make  up 
the  contour  of  the  bird,  are  contour  feathers.  The  great 
variation  seen  in  these  is  but  an  intimation  of  what  may  be 
expected  in  feathers  of  this  class. 

Down  feathers  lie  beneath  and  between  the  contour 
feathers.  Pluck  the  contour  feathers  one  by  one  from 
a  small  space  on  the  body,  and  the  down  feathers  will 
remain.  Examine  one  of  them  with  a  lens.  Compare  its 


220  VERTEBRATES. 

barbs  with  the  barbs  of  a  contour  feather.     What  is  the 
probable  use  of  these  down  feathers  ? 

There  are  certain  hairlike  feathers  (filoplumes)  on  the 
skin  of  birds.  These  are  easily  seen  on  a  plucked  fowl 
before  singeing.  They  are  not  hairs,  as  a  microscopic 
examination  of  one  will  prove.  Birds  do  not  have  true 
hairs. 

Other  Structures.  —  Separate  the  feathers  above  the 
base  of  the  tail,  and  find  the  oil  can,  a  double,  cone- 
shaped  gland,  which  secretes  an  oily  fluid  for  "feather 
dressing."  The  bird,  with  its  beak,  presses  a  drop  of  oil 
from  this  gland,  and  distributes  it  over  the  tips  of  the 
feathers,  in  the  familiar  act  of  preening. 

Examine  the  ear  again,  and  note  that  the  tympanic 
membrane  is  at  the  bottom  of  a  short  external  auditory 
meatus,  and  that  the  skin  of  the  head  dips  down  into  and 
lines  this  opening. 

Holding  the  back  of  the  head  firmly  with  one  hand, 
alternately  raise  and  depress  the  upper  mandible,  and 
observe  that  it  is  movable  upon  the  head. 

Within  the  mouth  find  the  single  guarded  opening  of 
the  nostrils.  Find  also  the  openings  into  the  esophagus 
and  into  the  glottis.  Note  the  shape  and  character  of  the 
tongue. 

Insert  a  tube  into  the  glottis,  and  inflate  the  lungs. 
Note  what  portions  of  the  body  are  expanded. 

Dissection.  —  Prepare  a  freshly  killed  specimen  for  dis- 
section. Fasten  the  specimen  with  tacks,  back  down- 
ward, on  a  shingle,  with  legs  and  wings  fully  extended. 
Part  the  feathers,  and  divide  the  skin  along  the  median 
ventral  line,  from  the  neck  to  the  tail,  taking  care  not  to 
cut  through  the  thin  abdominal  muscles.  Now  loosen 
the  skin  from  the  sides  of  the  body  by  holding  the 
severed  edge  of  the  skin  between  a  thumb  and  finger, 


THE   ENGLISH   SPARROW.  221 

and  with,  a  knife  blade  pushing  the  flesh  away  from  the 
skin.  At  the  anterior  end  of  the  first  cut  make  a  circu- 
lar cut  through  the  skin,  about  the  base  of  the  neck. 
Then  carefully  draw  the  skin  of  the  neck  forward  over 
the  head,  wrong  side  out,  and  fasten  it  with  a  tack  in 
front  of  the  beak.  While  doing  this,  observe  the  position 
assumed  by  the  retracted  neck,  and  note  again  how  much 
the  feathers  contribute  to  the  beauty  of  the  bird's  outline, 
and  improve  its  form  for  rapid  passage  through  the  air. 
Draw  the  skin  out  laterally  on  each  side  of  the  first 
median  cut,  and  fasten  it  away  from  the  sides  of  the 
body. 

Pass  a  tube  into  the  esophagus,  and  inflate  the  crop, 
a  capacious  expansion  of  the  esophagus  at  the  base  of 
the  neck.  Tie  a  string  about  the  esophagus  to  keep  the 
crop  inflated,  for  convenience  in  dissecting  off  the  fat  and 
integument  which  cover  it. 

Observe  on  each  side  of  the  neck  a  vein  (the  jugular 
vein),  usually  filled  with  blood,  and  dark-colored,  and 
close  beside  it  a  white  nerve  (the  vagus  nerve). 

I.  Removal  of  the  Body  Wall.  —  On  the  median  line  of 
the  breast  observe  the  ventral  edge  of  the  sharp  ridge 
(or  keel)  of  the  sternum,  and  on  either  side  of  it  the 
thick  muscles  which  cover  the  sternum.  Posterior  to  the 
sternum,  the  internal  organs  are  covered  only  by  the  thin 
wall  of  the  abdomen.  Sever  the  muscles  from  the  keel 
by  a  single  longitudinal  cut  on  each  side  of  it,  keeping 
the  knife  close  to  the  bone.  Continue  the  cuts  laterally 
around  the  posterior  edge  of  the  sternum,  severing  the 
attachment  (origin)  of  a  great  flap  of  muscle.  Lift  up 
the  loosened  posterior  end  of  this  great  muscle,  and 
observe  it  separating  from  a  smaller  muscle,  which  has 
its  origin  in  the  angle  between  the  horizontal  part  of 
the  sternum  and  the  keel.  The  larger  muscle  is  the 
pectoralis  major;  the  smaller  one,  the  pectoralis  minor. 


222  VERTEBRATES. 

Dissect  these  breast  muscles  free  from  all  attachments 
except  their  insertions,  and,  while  doing  so,  look  for 
veins,  arteries,  and  nerves,  entering  the  muscles  near  the 
shoulder. 

The  removal  of  the  pectoral  muscles  discloses  the  enor- 
mously developed  sternum,  with  its  sharp  keel  and  its 
lateral  ribs.  The  V-shaped  bone  in  front  of  the  sternum 
is  the  wiskbone  or  merrythought,  and  is  made  up  of  the 
two  clavicles  grown  solidly  together  at  their  inner  ends. 
The  paired  stout  bones  extending  from  the  shoulders 
to  articulate  with  the  anterior  end  of  the  sternum  are 
the  coracoids.  Disarticulate  and  entirely  remove  the 
clavicles.  Free  the  coracoids  from  the  sternum,  and  turn 
them  outward.  With  small  scissors  cut  away  the  exposed 
abdominal  wall,  and  cut  forward  through  the  ribs  at  the 
sides  of  the  sternum.  Then  remove  the  sternum,  avoiding 
blood  vessels  as  much  as  possible.  This  will  expose  the 
internal  organs.  Again  inflate  the  lungs  through  the  glot- 
tis, and  observe  the  large  air  sacs  in  the  abdomen,  commu- 
nicating with  them.  Remove  blood,  which  may  collect 
about  the  organs,  with  a  small  damp  sponge.  Moisten  the 
neck,  if  it  dries  and  hardens  too  rapidly. 

II.  The  Trachea. — Find  at  the  base  of  the  tongue  a 
small  U-shaped  hyoid  lone  surrounding  the  front  of  the 
glottis,  the  long  arms  of  the  U  extending  posteriorly 
behind  the  skull.  Dissect  it  and  the  tongue  free  from 
their  attachments  to  the  lower  jaw.  The  glottis  opens 
into  a  slightly  swollen  cartilaginous  antechamber  of  the 
trachea,  called  the  larynx.  At  the  posterior  end  of  the 
trachea,  where  it  divides  into  two  small  bronchi,  is  another 
slightly  swollen  portion  (the  syrinx).  This  latter  is  the 
principal  voice  organ  in  birds.  Cut  across  the  trachea 
half  an  inch  in  front  of  the  bronchi  into  which  it  divides. 
Make  a  lateral  cut  with  fine  scissors  along  the  sides  of 
the  trachea  and  bronchi,  and  turn  down  the  ventral  wall. 


THE  ENGLISH  SPARROW.  223 

Observe  the  thinner  walls  of  the  posterior  portions  of  the 
syrinx.  Observe  the  delicate  vertical  semilunar  mem- 
brane projecting  forward  into  the  syrinx  from  the  angle 
between  the  bronchi.  By  the  vibration  of  this  membrane, 
voice  is  produced. 

Note  the  relative  position  of  trachea  and  esophagus. 
How  is  the  food,  in  passing  through  the  mouth,  kept  from 
getting  into  the  trachea  through  the  glottis  ? 

III.  Organs  of  Digestion.  —  Dissect  out  and  remove  the 
trachea  and  anterior  ends  of  the  bronchi.  Then  proceed 
to  a  dissection  of  the  digestive  system,  disregarding  the 
cutting  of  blood  vessels ;  for  the  circulatory  system  will 
be  studied  later  in  an  injected  specimen. 

Trace  the  alimentary  canal,  beginning  at  the  mouth. 
The  large  crop,  in  the  midst  of  the  esophagus,  is  a  sort  of 
food  reservoir  in  which  the  comminution  of  ingested  food 
is  begun.  In  its  transparent  walls  may  be  seen  bands  of 
muscle  fibers,  which,  contracting,  give  to  the  crop  a  sort  of 
slow,  churning  motion  ;  and  this,  together  with  the  grind- 
ing action  of  the  gravel  usually  found  in  the  crop,  and  the 
softening  action  of  secretions  poured  from  glands  in  its 
walls,  begins  the  reduction  of  the  food. 

A  short  distance  posterior  to  the  crop,  the  backward  con- 
tinuation of  the  esophagus  enters  the  mottled  glandular, 
slightly  dilated  stomach. 

Close  behind  the  stomach  is  the  large  gizzard,  some- 
imes  called  the  muscular  stomach.  Note  the  shape  of 
this  organ,  the  satiny  luster  of  its  exterior,  the  thickness 
of  its  powerful  muscular  walls,  the  toughness  of  its  fibrous 
inner  coat,  and  the  fine  gravel  mixed  with  its  contents. 
This  gravel  takes  the  place  of  teeth,  and  assists  in  the 
final  reduction  of  the  food. 

The  intestine  immediately  succeeds  the  gizzard.  The 
first  long  loop  in  it  is  called  the  duodenum.  Into  this 
part  the  duct  from  the  inclosed  whitish  or  pinkish  pan- 


224  VERTEBRATES. 

creas  opens,  and  also  the  duct  from  the  gall  bladder,  which 
is  attached  beneath  the  edge  of  one  lobe  of  the  liver. 

Posteriorly  the  intestine  opens  into  a  widened  terminal 
portion  of  the  canal  (the  cloaca).  Near  the  end  of  the 
intestine  are  two  little  lateral  side  branches,  which  end 
blindly,  and  are  called  cceca  (or  diverticulce). 

Cut  off  the  esophagus  near  its  anterior  end,  and  the 
intestine  near  its  posterior  end.  Dissect  out  the  inter- 
vening part  of  the  alimentary  canal,  liver,  and  pancreas, 
noting  the  dark-red  spleen  lying  near  the  stomach,  the 
mesentery  looping  up  the  intestine,  and  the  blood  vessels 
distributed  to  all  the  parts. 

IV.  The  Heart.  —  Slit  open  the  pericardium.     Expose 
and  examine  the  heart.     Note  its  conical  shape,  and  the 
firmer  texture  of  its  more  muscular  posterior  end.     The 
auricles  (right  and  left)  at  the  anterior  end  are  distin- 
guishable from  the  ventricles  by  their  darker  color,  and 
by  being  marked  off  from  the  ventricles  and  from  each 
other  by  delicate  yellowish  lines  of  fat.     Prick  a  hole  in 
each  auricle,  insert  a  pipette,  and  inflate  to  see  their  extent. 

That  there  are  two  ventricles  also  (right  and  left),  is 
not  evident  from  the  exterior.  Snip  off  the  posterior  end 
of  the  heart  with  sharp  scissors,  and  look  at  the  cut  sur- 
face. The  cavities  of  the  two  ventricles  will  be  at  once 
apparent,  —  that  of  the  left  ventricle  circular,  and  sur- 
rounded by  very  thick,  muscular  walls ;  that  of  the  right 
ventricle,  crescent-shaped,  and  with  thinner  walls.  Dis- 
sect out  the  heart  and  its  connecting  blood  vessels, 
and  fully  expose  the  lungs. 

V.  The  Lungs.  —  Pass  a  bristle  into  one  of  the  lungs 
through  its  bronchus,  and   probe   to   find  the   openings 
by   which    the    lungs    communicate   with    the    air   sacs. 
Lay  open  the  bronchus  with  fine   scissors,  and  see   how 
it   is   branched,    and    how   its   branches   are    distributed 
through  the  lung.     Dissect  out  the  lungs,  and  note  how 


THE   ENGLISH   SPARROW.  225 

closely  they  are  fitted  into  the  dorsal  part  of  the  body 
cavity,  and  how  deeply  they  are  indented  by  the  ribs. 

VI.  Renal  and  Reproductive  Organs.  —  There  yet  re- 
main in  the  posterior  dorsal  part  of  the  body  cavity  the 
brownish,  trilobed  kidneys,  partly  hidden  by  the  repro- 
ductive organs,  —  a  pair  of  roundish  or  oval,  light-colored 
testes,  in  the  male ;  a  single,  larger  ovary,  often  showing 
developing  eggs,  in  the  female.  All  these  organs  com- 
municate by  separate  ducts  with  the  cloaca.  Remove 
the  kidneys,  noting  their  relations  to  the  pelvic  bones 
and  to  the  sacral  spinal  nerves. 

Concluding  Work.  —  Find  two  regions  in  the  spinal 
column  in  which  the  vertebrae  are  wider  than  in  other 
parts.  Observe  that  the  spinal  nerves  issuing  in  these 
regions  are  larger  than  the  others.  To  what  parts  are 
these  spinal  nerves  distributed? 

Cut  the  skin  around  the  base  of  one  of  the  legs,  and 
pull  it  off  like  a  stocking  wrong  side  out.  Dissect  apart 
the  muscles  to  find  the  mechanism  by  means  of  which  the 
toes  are  clasped  automatically  when  the  bird  sits  perch- 
ing. Of  what  advantage  is  this  to  the  bird  ? 

Loosen  the  bird,  turn  it  over,  and  pull  the  skin  entirely 
off  from  the  head.  The  pockets  in  the  skin,  which  are 
fitted  down  into  external  auditory  openings,  may  readily 
be  pulled  out,  but  the  attachment  at  the  eyes  will  have  to 
be  cut.  Then  carefully  cut  away  the  top  of  the  cranium, 
and  the  membranes  that  lie  beneath  it,  closely  covering 
the  brain.  Having  fully  exposed  the  brain,  carefully 
lift  it  out,  beginning  at  the  anterior  end,  and  severing 
the  cranial  nerves  as  soon  as  they  are  exposed.  Place  the 
brain  at  once  in  alcohol  to  harden  for  future  study. 

Study  of  the  Circulatory  System. — In  an  injected 
specimen1  study  the  circulatory  organs.  The  heart  has 

1  For  method  of  injection  see  Appendix,  p.  286. 

NEED.   ZOOL.  — 15 


226  VERTEBRATES. 

already  been  studied,  and  its  auricles  and  ventricles  have 
been  located. 

I.  The  Venous   System.  —  Trace  first  the  veins.     The 
right  auricle  receives  all  the  venous  blood  from  all  parts 
of   the   body  through   three   principal  veins, — two  prce- 
cavce  (right  and  left)  and  one  postcava.     Find  these  three 
veins,  and  note  the  points  at  which  they  enter  the  auricle. 
Trace  each  of  the  praecavse  forward,  and  find  each  to  be 
formed  by  the  confluence  of  three  veins,  one  coming  from 
the  head  (the  jugular),  one  from  the  wing  (the  brachial), 
and  one  from  the  great  pectoral  muscles  (the  pectoral). 
Observe  that  the  postcava  comes  to  the  heart  through  the 
right  lobe  of  the  liver,  receiving  small  branches  in  that 
organ.     Posterior  to  the  liver  it  is  formed  by  the  union 
of   two  (iliac)  veins  coming   from  the  kidneys.     Three 
other  veins  on  each  side  bring  the  blood  from  the  posterior 
parts  of  the  body  to  the  kidneys. 

II.  The  Pulmonary  System.  —  The  blood  collected  in  the 
right  auricle  descends  through  a  valvular  opening  into  the 
right  ventricle.     The  right  ventricle  then  contracts,  and 
sends  the  blood  out  to  the  lungs  through  a  pair  of  short 
pulmonary  arteries  (right  and  left).     Find  these  arising 
together  from  the  right  auricle,  but  at  once  dividing,  and 
going  directly  one  to  each  lung. 

From  the  lungs  the  blood,  after  aeration,  flows  back  to 
the  heart  through  a  pair  of  pulmonary  veins  (right  and 
left),  which  enter  the  left  auricle  separately.  These  will 
probably  be  more  easily  traced  from  the  auricle  out  to  the 
lungs. 

III.  The  Arterial  System. — The  blood  thus  collected 
into  the  left  auricle  descends  through  a  valvular  opening 
into  the  left  ventricle,  whence  it  is  expelled  through  a 
single  large  artery  (the  aorta)  to  all  parts  of  the  body  by 
the  contraction  of  the  ventricle.     Herein  lies  the  explana- 
tion of  the  very  thick  muscular  walls  of  this  ventricle. 


THE   ENGLISH   SPARROW.  227 

Near  its  origin  the  aorta  gives  off  a  pair  of  large  (in- 
nominate) branches,  which  go  to  right  and  left  sides  of 
the  anterior  part  of  the  body.  Each  of  these  branches 
divides  into  three  smaller  arteries  (carotid,  brachial,  and 
pectoral),  corresponding  to  the  three  branches  of  each 
prsecava.  The  aorta  curves  dorsally,  and  toward  the  right 
side,  and  is  continued  posteriorly  through  the  body  cavity 
as  the  dorsal  aorta,  giving  off  principal  branches  to  all  the 
important  visceral  organs,  and  to  the  legs. 

The  Skeleton.  —  Study  the  sparrow's  skeleton  from  dis- 
articulated bones.  Have  a  mounted  skeleton  at  hand  for 
reference.  Note  the  lightness  of  the  bones.  Hold  some 
of  them  up  to  the  light,  and  observe  the  air  spaces  in 
them.  Note  that  the  most  striking  peculiarities  of  the 
skeleton  are  in  the  bones  of  the  pectoral  and  of  the  pelvic 
regions,  modifications  in  the  one  region  adapting  the  fore 
limbs  for  flight,  and  in  the  latter  adapting  the  hind  limbs 
for  supporting  the  entire  weight  of  the  body  in  walking. 

The  axial  part  of  the  skeleton,  as  in  all  vertebrates,  is 
the  spinal  column,  with  the  skull  at  its  anterior  end. 

I.  The  Skull.  —  Study  the  skull.  Observe  the  large 
orbits  dividing  it  into  a  posterior  cranial  region  and  an 
anterior  facial  region.  Observe  that  the  orbits  are  sepa- 
rated from  each  other  by  an  incomplete  interorlital  septum. 
Observe  that  the  cranial  cavity  opens  widely  into  the 
posterior  dorsal  part  of  both  orbits.  This  large  opening 
was  closed  in  life  by  a  membrane,  but  the  smaller  ones 
beneath  it  are  foramina  for  the  exit  of  cranial  nerves. 
At  the  back  of  the  cranium  find  the  foramen  magnum,  and 
just  beneath  this  the  single  occipital  condyle,  a  minute 
knob  of  bone  for  articulation  with  the  first  vertebra. 
On  either  side  of  the  condyle  are  very  minute  foramina 
for  the  exit  of  other  cranial  nerves. 

Note  how  the  lines  of  the  skull  converge  toward  the 


228 


VERTEBRATES. 


point  of  the  beak,  giving  the  skull  a  slightly  oblique, 
pyramidal  form,  the  cranium  forming  the  base  of  the 
pyramid. 

The  skull  is  composed  of  many  bones,  a  large  proportion 
of  which  will  be  found  to  be  solidly  coossified  in  all  except 

immature  specimens.    Their  out- 

lines will  not  be  distinguishable, 
5 

but  their  location  may  be  learned 
by  reading  the  following  descrip- 
tion with  skull  in  hand. 

The  region  immediately  sur- 
rounding the  foramen  magnum 
is  formed  of  the  occipital  bones. 

Four  pairs  of  bones  complete 
the  dorsal  surface  of  the  skull. 
The  bones  of  each  pair  meet  on 

the  median  line. 

^     The  parieM  bmes  form  the 

greater  part  of  the  roof  of  the 
cranium,  and  present  convex  dor- 

sal  SUrf  aCCS. 

2-  In  front  of  these' 


SKULL  OF  SPARROW,  slightly 
enlarged  (ventral  view,  man- 
dible removed) :  m,  foramen 
magnum;  c,  occipital  con- 
dyle;  bs,  basisphenoid ;  r, 


bar  ;  q,  quadrate  ;  ptg,  ptery- 


lary  portion  of  quadratojugai  tal  bones  cover  the  foremost  part 

ptpaSeTroc^'o/^  of  the  cranial  cavity,  and  form 

maxillary;  pr  m,  maxillary  the  upper  boundary,  and  most  of 

SStSTSSSfLS  the   posterior  boundary,   of  the 

cranial  cavity  (closed  in  life    orbits. 

3.  The  nasal  bones  lie  next  in 

front  of  the  frontals,  and  extend  forward  between,  and 
partly  surround  posteriorly,  the  nasal  openings. 

4.  The  premaxillary  bones  complete  the  dorsal  surface, 
and  form  the  bony  part  of  the  upper  mandible. 

Looking  at  the  side  of  the  skull,  note  :  — 

1.  The  lachrymal  bone,  of  irregular  rhomboidal  outline, 
set  transversely  to  form  the  anterior  wall  of  the  orbit. 


THE   ENGLISH   SPARROW.  229 

2.  The  postorbital  process  of  the  frontal  bone,  projecting 
downward  to  form  the  postero-lateral  rim  of  the  orbit. 

3.  The  squamosal  bone,  applied  obliquely  to  the  side  of 
the  cranium,  just  behind  the  postorbital  process  of   the 
frontal. 

4.  The  quadrate  bone,  a  conspicuous  bone  connecting 
the  lower  jaw  with  the  cranium,  and  freely  articulated 
with  both. 

On  the  ventral  surface  of  the  skull,  anterior  to  the  occip- 
ital, are  three  distinguishable  unpaired  bones. 

1.  The   basisphenoid   forms   the   convex,  most  ventral 
portion  of  the  cranium. 

2.  The  rostrum  is  the  narrow  forward  continuation  of 
the  basisphenoid,  and  appears  as  a  thickening  of  the  ven- 
tral edge  of  the  interorbital  septum. 

3.  The  ethmoid  is  a  small  bone  inclosed  between  the 
nasals  and  the  lachrymals,  and  lying  on  the  median  line, 
at  the  anterior  end  of  the  rostrum. 

The  remaining  bones  of  the  ventral  side  of  the  skull  are 
paired.  They  form  two  bony  bars  on  each  side,  extending 
from  the  premaxillary  in  front  to  the  quadrate  behind. 
The  premaxillary  of  each  side  on  its  ventral  surface  will 
be  seen  to  send  back  two  short  horizontal  processes  of  bone, 
one  to  meet  each  of  these  bars. 

1.  The  outer  or  quadratojugal  bar  is  a  slender  rod  of 
bone  forming  the  ventral  border  of  the  orbit.     It  extends 
from  the  outer  or  maxillary  process  of  the  premaxillary 
bone  to  the    quadrate.     It  is  composed  of   three  bones 
wholly  indistinguishable  in  the  adult  skull.      These  are 
(named   from  the   front)    maxilla,  jugal,    and    quadrato- 
jugal. 

2.  The  inner  or  palato-pterygoid  bar  is  composed  of  the 
palatine  and  pterygoid  bones,  and  extends  from  the  inner 
or  palatine  process  of  the  premaxillary  back  to  the  quad- 
rate.    It  is  not  a  straight  and  simple  bar  of  bone,  like  the 


230  VERTEBRATES. 

quadratojugal  bar,  but  irregular,  widely  and  irregularly 
expanded  in  its  anterior  part,  and  bent  inward  to  fit 
against  the  rostrum. 

The  two  bones  composing  this  bar  are  readily  distin- 
guishable. The  palatine  is  the  broad,  flat,  anterior  one 
which  meets  the  rostrum  by  its  inner  edge.  The  pterygoid 
is  the  slender,  posterior  one,  which  has  its  inner  end  ex- 
panded to  fit  against  the  side  of  the  rostrum,  its  outer  end 
rounded  for  articulation  with  the  quadrate. 

Thus  it  will  be  seen  that  both  upper  and  lower  mandibles 
are  articulated  to  the  cranium  by  the  quadrate.  The  other 
attachment  of  the  upper  mandible  to  the  cranium  is  in  the 
region  of  the  nasal  bones.  Holding  the  cranium  between 
the  fingers,  gently  move  the  mandible  up  and  down,  and 
observe  that  the  flexibility  of  the  bones  in  this  region, 
and  not  a  distinct  articulation,  permits  this  motion.  While 
moving  the  mandible,  observe  that  the  palatine  and  ptery- 
goid slide  forward  and  backward  upon  the  rostrum,  and 
the  lower  exterior  corner  of  the  lachrymal  slides  upon  the 
maxillary. 

A  pair  of  minute  bones  (the  vomers)  meet  on  the  median 
line  between  the  palatine  processes  of  the  two  premaxil- 
laries,  and  in  front  of  the  two  palatine  bores.  These  are 
liable  to  be  removed  in  the  preparation  of  the  skull,  and 
so  may  not  be  found. 

II.  The  Spinal  Column.  —  Study  the  spinal  column. 
Note  the  length  and  flexibility  of  the  neck,  the  shortness 
of  the  tail,  and  the  large  number  of  anchylosed  vertebra 
which  meet  the  bones  of  the  pelvic  arch. 

Four  regions  are  distinguishable  in  the  spinal  column, 
but  the  boundaries  between  them  are  ill  defined.  Named 
from  the  front,  these  are  the  cervical,  thoracic,  sacral,  and 
caudal  regions. 

The  cervical  vertebrae  are  those  between  the  head  and 
the  foremost  vertetra  bearing  a  rib  articulating  with  the 


THE   ENGLISH   SPARROW.  231 

sternum.     Study  a  typical  vertebra  from  near  the  middle 
of  the  cervical  region.     Note  :  — 

1.  Its  relatively  light  centrum. 

2.  Its  wide,  neural  arch,  notched  before  and  behind, 
with  the  neural  spine  small  or  absent. 

3.  Its   articular    processes    (zygapophyses).      How   do 
these  meet  in  adjacent  vertebrae? 

4.  The  saddle-shaped,  articular  faces  of  the  centrum. 

5.  The  wide,   transverse  processes  at  the  sides  of  the 
anterior  end,  each  perforated  at  its  base  by  a  wide  fora- 
men, and  produced  posteriorly  into  a  long,  slender  point. 
This  process  is  homologous  with  the  ribs  which  arise  in 
the  same  position  on  the  vertebrae  farther  back. 

The  thoracic  vertebrce  are  those  which  bear  ribs  articu- 
lating with  the  sternum.  Note  the  Y-shaped  processes 
uniting  the  tops  of  the  neural  spines  of  these  vertebrae. 
Observe  on  all  the  vertebrae  the  lateral  notches  opposite 
the  neural  canal,  for  the  exit  of  the  spinal  nerves. 

These  thoracic  ribs  consist  of  two  portions  :  — 

1.  A  vertebral  portion,  flattened  and  curved,  having  two 
articulating  surfaces  at  its  proximal  end, — a  head  which 
articulates  with  the  centrum  of  the  vertebra,  and  a  tuber- 
cle which  articulates  with  the  transverse  process,  —  and 
having  a  flattened  uncinate  process  which  projects  back- 
ward, overlapping  the  next  succeeding  rib. 

2.  A  sternal  portion,  slender  and  nearly  straight,  ex- 
tending obliquely  forward  to  articulate  with  the  sternum. 

Of  what  advantage  is  the  joint  in  the  middle  of  the 
rib  ?  The  series  of  overlapping  uncinate  processes  ? 

The  sacral  vertebrce  succeed  the  thoracic,  and  are  solidly 
anchylosed,  and  support  the  bones  of  the  pelvis.  Observe 
that  the  first  three  and  the  last  four  of  these  have  their 
lateral  processes  directed  laterally,  but  in  the  intervening 
three  or  four  these  processes  are  directed  dorsally. 

The  caudal  vertebrce  are  the  remaining  free  ones,  with 


232  VERTEBRATES. 

conspicuous  neural  and  lateral  processes,  and  the  large, 
terminal,  triangular  pygostyle  which  supports  the  tail 
feathers  (rectrices). 

How  many  cervical  vertebrae  are  there  ?  How  many  of 
them  bear  evident  ribs  ?  How  many  thoracic  vertebrae  are 
there?  How  many  thoracic  ribs  bear  uncinate  processes? 
How  many  sacral  vertebrae  are  there  ?  How  many  caudal  ? 

III.  The  Sternum.  —  Study  the  sternum.  Note  the  fol- 
lowing parts  :  — 

1.  A  large,  squarish,  shovel-shaped 
body,  which  closely  covers  the  tho- 
racic cavity,  and  extends  backward 
some  distance  over  the  abdomen. 

2.  A  large,  triangular  keel,  borne 

on  the  median  ventral   line   of   the 
STERNUM  OF  SPARROW 

FROM    RIGHT    SIDE     body  of  the  sternum.    Note  that  both 


(natural    size)  :     b,     ^  body  and  ^Q  keel  are  composed 

body  ;  k,  keel  ;  m,  ma-  •*     .  f 

nubrium  or  rostrum  ;     oi  very  thin  plates  ot  bone,  with  sur- 
cg,  coracoid  groove;     faceg    minutely    roughened    for    the 

cp,  costal  process;  x, 

lateral  xiphoid   pro-     attachment  of  muscles,  and  strength- 

cess  ;  sp,  space  filled  d  b     thickened  marcnns. 

in  life  by  membranes.  * 

3.  A   stout,    median   rostrum    (or 

manubrium),  forked  at  its  tip,  which  projects  forward, 
and  obliquely  upward  from  the  base  of  the  keel,  at  the 
front  of  the  body  of  the  sternum. 

4.  A  pair  of  sharp,  triangular  costal  processes  project- 
ing forward  from  the  anterior  angles  of  the  body.     The 
lateral  borders  of  these  processes  are  thickened  to  form 
the  costal  surfaces  bearing  facets  for  articulation  with  the 
sternal  ends  of  the  ribs. 

5.  Between  the  costal  processes   and   the   rostrum,  a 
pair  of  coracoid  grooves,  in  the  anterior  edge  of  the  body 
of  the  sternum,  meeting  on  the  median  line.    These  grooves 
are  for  articulation  with  corresponding  ridges  on  the  ends 
of  the  coracoid  bones. 


THE    ENGLISH   SPARROW. 

6.  Just  behind  the  costal  processes,  a  pair  of  conspicu- 
ous, slender  lateral  xiphoid  processes,  arising  from  the 
lateral  margins  of  the  body,  and  extending  obliquely 
backward,  to  partially  inclose  a  pair  of  triangular  spaces 
which  were  in  life  closed  by  membrane. 

IV.  The  Shoulder  Girdle.  —  Study  the  shoulder  girdle. 
Each  half  of  it  consists  of  the  three  usual  bones,  meeting 
to  form  the  shoulder. 

1.  The  scapula  is  a  long,  thin,  and  narrow  bone,  shaped 
somewhat  like  a  sled  runner,  extended  backward  from  the 
shoulder  above  the  ribs.     It  is  enlarged  to  form  articular 
facets  at  the  shoulder,  and  sharply  pointed  at  the  posterior 
end. 

2.  The  coracoid  is  a  stout,  straight  bone  set  in  between 
the  shoulder  and  the  front  of  the  sternum.     How  does 
its  direction  correspond  with  the  direction  in  which  the 
pectoral  muscles  pull  ? 

3.  The  clavicle  is  a  slender  bone,  shaped  like  a  fishhook, 
with  the  hook  turned  toward  the  sternum.     It  is  anchy- 
losed  at  its  hook  end  with  its  fellow  of  the  opposite  side, 
and  the  two  together  are  commonly  known  as  the  fur- 
culum  (merrythought,  or  wishbone). 

V.  Wing  Bones.  —  Study  the  bones  of  the  wing. 

1.  The  humerus  is  the  single  stout  bone  of  the  arm. 

2.  The  radius  and  ulna  are  the  two  bones  of  the  fore- 
arm.    They  are  entirely  separate.    The  ulna  is  much  the 
stouter.     It  has  a  blunt  proximal  (olecranori)  process  pro- 
jecting back  of  the  elbow  joint,  and  its  posterior  edge  is 
roughened  for  the  attachment  of  the  bases  of  the  second- 
ary quills. 

3.  The  carpal,  metacarpal,  and  pJialangeal   bones  are 
peculiarly  anchylosed  in  the  adult.     Two  carpal  bones 
remain  free  at  the  distal  end  of  radius  and  ulna.     Three 
distal  carpal  bones  have  fused  with  three  metacarpals  to 
form   a   conspicuous   single   bone,  the    carpo-metacarpus. 


234 


VERTEBRATES. 


The  two  component  parts  of  this  bone  most  easily  recog- 
nizable are  the  elongated  second  and  third  metacarpals  ; 
the  second  is  stout  and  straight,  the  third  is  slender  and 
curved,  and  the  two  are  fused  only  at  their  ends.  The 
short  and  stumpy  phalanges  of  three  rudimentary  digits 
are  articulated  with  the  carpo-metacarpus,  —  one  (the 
thumb)  at  its  anterior  edge  near  its  proximal  end,  the 
other  two  toward  its  distal  end. 


WING  BONES  OF  SPARROW,  slightly  enlarged  (ventral  aspect  of  left  wing) : 
h,  humerus ;  r,  radius ;  u,  ulna ;  ol,  olecranon  process  of  the  ulna ;  c  and  c, 
free  carpal  hones ;  cmc,  carpo-metacarpus ;  1,  2,  and  3,  phalanges. 

VI.  The  Pelvic  Girdle.  —  Study  the  pelvic  girdle.  Each 
half  of  it  is  made  up  of  the  three  usual  bones,  —  ilium, 
ischium,  and  pubis,  —  meeting  around  the  acetabulum, 
and  solidly  anchylosed  together.  The  acetabulum  is 
but  a  rim  of  bone,  its  bottom  being  membranous. 

1.  The  ilium  forms  the  front  and  upper  walls,  and  a 
great  part  of  the  hinder  wall  of  the  acetabulum.     The  two 
ilia,  together  with  the  sacral  vertebrae  included  between 
them,  form  the  entire  roof  of  the  pelvis.    Each  ilium  is 
attached  along  almost  its  entire  length  to  the  lateral  pro- 
cesses of  the  sacral  vertebra.      An  obliquely  transverse 
line  divides  its  dorsal  surface  into  two  parts,  the  anterior 
one  concave,  the  posterior  one  convex.     A  lateral  process 
from  it  overhangs  the  acetabulum,  and  articulates  with  a 
process  on  the  femur. 

2.  The  ischium  forms  a  part  of  the  hinder  wall  of  the 
acetabulum,  and  extends  thence  directly  backward.     It  is 


THE   ENGLISH   SPARROW.  235 

In  part  separated  from  the  ilium  by  a  large  oval  or  oblong 
{ilio-*ciatic)  foramen. 

8.  The  pubis  forms  part  of  the  lower  wall  of  the  ace- 
tabulum,  and  extends  thence  obliquely  downward  and 
backward.  It  is  in  part  separated  from  the  ischium  by  a 
small,  round  (obturator)  foramen. 

VII.   Leg  Bones.  —  Study  the  bones  of  the  leg. 

1.  The  femur  is  the  single  bone  of  the  thigh. 

2.  The  tibia  is  the  large  bone  of  the  shank ;  the  fibula 
is  the  slender  bone  extending  halfway  down  the  outer  side 
of  the  tibia.     The  proximal  tarsal  bones  are  fused  with 
the  distal  end  of  the  tibia,  leaving  the  ankle  joint,  not 
between  tibia  and  tarsal  bones,  but  between  the  first  and 
second  series  of  tarsal  bones. 

3.  The  tarsal  bones  of  the  second  series  are  fused  with 
the  metatarsal  bones,  to  form  the  single  bone  which  we 
have  already  designated  as  the  tarsus  (more  strictly,  the 
tarso-metatarsus) . 

At  the  distal  end  of  the  tarsus  are  the  four  toes.  The 
hind  toe  is  the  first  digit ;  the  others  are  numbered  second, 
third,  and  fourth,  away  from  the  median  plane  of  the  body. 
How  many  phalanges  are  there  in  each  digit? 

The  Brain.  —  Study  the  external  features  of  the  brain. 
On  the  dorsal  surface,  note  the  parts  seen,  proceeding 
from  the  front,  as  follows  :  — 

1.  A  pair  of  small,  conical,  olfactory  lobes,  at  the  ante- 
rior end. 

2.  A  pair  of  large,  smooth,  pear-shaped  cerebral  hemi- 
spheres, meeting  on  the  median  plane. 

3.  A  small,  median,  pineal  body,  immediately  behind  the 
hemispheres,  and  in  the  angle  between  them. 

4.  A  pair  of  smooth,  ovoid,  optic  lobes,  behind  and  below 
the  hemispheres. 

5.  A   median,  oval    cerebellum,  transversely  furrowed, 


236  VERTEBRATES. 

i 

meeting  the  hemispheres  in  front,  and  overlapping  the 
optic  lobes  at  each  side. 

6.  A  large  medulla,  covered  in  front  by  the  cerebellum, 
and  narrowed  posteriorly  into  the  spinal  cord. 

On  the  ventral  surface  note  the  crossing  of  the  optic 
nerves  (optic  cJiiasma),  and  just  behind  this,  on  the  median 
line,  a  small  process  (the  infundibulum),  which  was  con- 
nected with  the  pituitary  body  before  the  removal  of  the 
brain. 

The  sparrow  is  a  representative  of  the  vertebrate  class 
Aves  (or  birds). 

Other  Birds.  —  If  material  is  at  hand,  and  if  time  will 
permit,  the  further  study  of  this  interesting  and  important 
group  is  recommended.  A  hawk,  a  duck,  a  woodpecker, 
and  a  snipe  are  in  most  places  obtainable  ;  and  these  four 
are  mentioned  for  further  study,  because  they  illustrate 
common  types  of  bird  structure.  It  will  be  interesting  to 
compare  a  number  of  birds  as  to  the  following  points  of 
structure,  noting  in  each  case  the  exact  adaptation  of  each 
structural  peculiarity  to  the  life  and  habits  of  the  bird  in 
which  it  is  found.  Note  :  — 

1.  The  relative  size  and  proportions  of  body,  wings,  and 
tail. 

2.  The  character  of  the  plumage. 

3.  The  shape,  size,  and  strength  of  leak  and  claws. 

4.  The  number,  insertion,  and  direction  of  the  toes,  and 
the  amount  of  webbing  between  them. 

5.  The  length  and  position  of  the  neck  and  of  the  legs. 

6.  The  size  and  position  of  the  eyes. 
In  the  field,  note  :  — 

1.  Their  haunts. 

2.  Their  food,  and  manner  of  obtaining  it. 

3.  Their  flight .     Learn  to  know  a  bird  by  this  alone. 
The  rapid,  whistling  flight  of  some  ducks ;    the  cycloid 


THE    RABBIT.  237 

soaring  of  some  hawks  ;  the  airy,  skimming  flight  of  swal- 
lows ;  the  shambling,  silent  flight  of  owls ;  the  graceful 
sweeps  made  by  the  large  woodpeckers  between  distant 
trees;  the  flitting  of  warblers,  etc.,  —  are  very  character- 
istic. 

4.  Their  notes.     Learn  to  recognize  a  bird  by  its  voice 
alone.     Learn  to  recognize  the  meaning  in  the  different 
notes  of  some  familiar  birds. 

5.  Their  attitudes.     By  the  position  in  perching  alone 
most  birds  may  be  known. 

6.  Their  nests.     Observe  the  time  of  nesting ;  the  num- 
ber, size,  color,  and  markings  of  the  eggs  ;  and  the  loca- 
tion, material,  and  construction  of  the  nests. 

7.  The  times  of  departure  and  return  of  the  migratory 
species. 

If  a  small  collection  of  bird  skins  is  at  hand,  the  work 
of  identifying  the  species  in  it  is  commended  as  an  excel- 
lent means  of  getting  a  practical  acquaintance  with  the 
leading  systematic  peculiarities  of  a  number  of  birds.1 


THE  RABBIT. 

(Lepus  syluaticus.) 

Haunts.  —  This  animal  lives  in  hedges,  brush  heaps, 
and  brier  patches  on  the  borders  of  fields,  orchards,  and 
gardens.  It  is  much  hunted  for  food,  and  throughout  the 
winter  may  usually  be  found  in  the  market.  But  market 
specimens  are  usually  so  mutilated  as  to  be  unfit  for  study. 
Specimens  for  study  may  be  easily  captured  alive  by 

1  Should  any  student  wish  to  prepare  a  few  bird  skins  for  study,  he  will 
find  full  directions,  well  illustrated  by  plates,  in  Davie's  Methods  in  the 
Art  of  Taxidermy.  For  further  study,  Coues's  Key  to  North  American 
Birds,  and  Davie's  Nests  and  Eggs  of  North  American  Birds,  are 
recommended. 


238  VERTEBRATES. 

trapping.  Light  steel  traps  are  usually  efficient;  but  a 
heavily  weighted  box  trap  set  with  a  figure-4  trigger, 
and  baited  with  a  cabbage  stalk  or  a  sweet  potato,  will 
answer  equally  well.  As  the  rabbit  is  nocturnal,  the 
traps  should,  of  course,  be  set  in  the  evening,  and  in  places 
much  frequented  by  rabbits,  in  the  "  runs  "  or  paths  they 
make  through  the  grass  or  through  the  snow. 

Habits.  —  A  little  time  will  be  well  spent  in  studying 
the  rabbit  in  its  relation  to  nature.  A  moonlight  evening 
in  winter,  when  the  ground  is  frozen  and  covered  with 
snow,  and  when  food  has  become  scarce,  or  hard  to  get, 
will  afford  a  good  opportunity.  At  such  a  time  the 
rabbits  become  more  venturesome  in  their  search  for  food. 
They  invade  gardens,  and  search  them  over  for  stray  tops 
of  cabbage  or  celery  left  from  the  preceding  autumn ; 
they  enter  orchards,  and  gnaw  the  bark  from  unprotected 
young  apple  trees;  they  girdle  wild  crab  apples  and 
other  small  woodland  trees  in  the  same  way;  and  they 
sometimes  assemble  and  play  together,  dancing  and  scam- 
pering about  in  the  snow,  with  no  other  apparent  object 
than  a  good  social  time. 

On  a  warm  evening  in  spring  they  may  be  seen  sitting 
by  the  roadside,  nibbling  the  tender  leaves  of  clover.  At 
such  a  time  they  may  be  approached  quietly.  If  alarmed, 
they  will  at  once  leap  into  cover,  and  disappear.  In  locali- 
ties where  they  are  much  hunted  on  foot,  they  may  be 
approached  nearer  on  horseback. 

At  a  distance,  one  may  often  be  seen  to  rise  up  on  its 
hind  feet  to  its  full  length,  and  look  about,  as  if  for 
danger,  with  ears  aloft.  Near  at  hand,  one,  wishing  to 
hide,  will  crouch  low  on  the  ground,  with  its  ears  ex- 
tended flat  along  its  back.  In  such  a  position  it  is  very 
inconspicuous,  especially  if  seen  among  dried  grass  and 
leaves,  which  its  colors  so  closely  imitate. 


THE   BABBIT. 


239 


In  a  rabbit  hunt  with  dogs,  a  rabbit  will  certainly  be 
seen  to  run  in  circles,  repeatedly  crossing  its  former  tracks, 
throwing  the  dogs  off  the  scent. 

The  simple  "  form "  the  rabbit  makes  for  itself  for  a 
resting  place  in  the  grass  ;  the  retreats  it  finds  in  hol- 
low logs  and  stumps,  and  in  the  deep  burrows  of  other 
animals ;  and  the  shallow,  fur-lined  burrow  which  it  makes 
for  itself  in  dry,  loose  soil,  for  a  home  in  which  to  rear 
its  interesting  brood,  — 
should  all  be  studied  in 
the  field. 

The  live  rabbit  should  be 
studied  in  the  laboratory. 
Its  postures  should  be 
noted.  It  should  be  deter- 
mined whether  the  rabbit 
ever  walks,  how  fore  feet 
and  hind  feet  are  used  in 
locomotion,  in  what  direc- 
tion it  cannot  see  without 
turning  its  head,  whether 
it  shifts  its  ears  to  suit 
the  direction  from  which 

a  sound  is  coming,  etc.  GRAY  EABBIT  (Lepus  sylvaticus). 

External  Features. — Note  its  covering  of  hair.  Ob- 
serve that  the  hairs  are  of  three  principal  sorts  :  — 

1.  Short,  soft,  kinky  hairs,  which  make  up  the  greater 
part  of  its  coat,  and  which  collectively  constitute  fur. 

2.  Fewer,  longer,  straight,  black-tipped   hairs,  which 
protrude  through  the  fur. 

3.  Long,  stiff,  tactile  hairs  (or  whiskers)  at  the  sides  of 
the  upper  lip,  and  above  and  below  the  eyes,  deep  seated 
in  the  skin,  and  intimately  connected  with  nerve  endings. 

Note  the  color  of  the  fur  at  the  surface,  and  next  the 


240  VERTEBRATES. 

skin.  On  what  parts  of  the  body  is  the  hair  longest  ? 
What  exposed  parts  are  bare,  and  why  ?  Compare  the 
color  of  upper  and  lower  surfaces.  What  is  the  character 
of  the  hair  on  the  soles  of  the  feet  ? 

Examine  the  claws.  Are  they  well  adapted  for  weapons 
of  offense  ? 

Note  the  length  and  position  of  the  tail.  Take  the  fol- 
lowing measurements  :  the  distance  from  the  tip  of  the 
nose  to  the  base  of  the  tail ;  the  length  of  the  tail ;  the 
height  of  the  ears  ;  the  length  of  fore  and  hind  legs  and 
of  fore  and  hind  feet. 

Note  the  close  approximation  of  the  ears,  and  the  wide 
space  between  the  eyes.  What  is  the  advantage  to  the 
rabbit,  of  this  arrangement? 

Why  does  a  rabbit  run  more  easily  up  hill  than  down  ? 

Note  that  the  upper  lip  is  cleft  below  the  nostrils,  ex- 
posing the  front  teeth  when  the  lips  are  retracted.  The 
advantage  of  this  in  gnawing  is  very  obvious. 

Structure.  —  Dissect  the  rabbit  on  a  broad  piece  of 
board,  into  which  tacks  may  be  driven.  Use  an  injected 
specimen.1  Make  a  circular  cut  through  the  skin,  around 
the  base  of  its  neck,  and  pull  the  skin  forward  over  its 
head,  wrong  side  out,  carefully  dissecting  it  free  from  the 
parts  which  lie  beneath.  At  the  base  of  the  ears  note 
the  tubular,  basal  cartilage  supporting  each  ear,  and  see 
also  the  attached  muscles,  which  change  the  position  of 
the  ears.  Cut  off  the  ears  :  this  will  expose  the  external 
auditory  canals.  At  the  eyes,  in  removing  the  upper  and 
lower  lids  with  the  skin,  an  imperfect  third  eyelid  (or 
nictitating  membrane)  should  be  left  behind.  Remove  the 
skin  of  the  head  entirely,  breaking  or  cutting  its  attach- 
ments at  the  lips.  Note  the  hairiness  of  the  inside  of  the 
cheeks. 

1  For  a  method  of  injection  see  Appendix,  p.  286. 


THE   RABBIT.  241 

I.  The  Teeth.  —  Placing  the  rabbit  on  its  side,  lay  open 
the  cavity  of  the  mouth  by  a  lateral  cut  midway  between 
upper  and  lower  jaws.  This  will  expose  the  teeth.  Ob- 
serve that  the  teeth  are  of  two  sorts  :  — 

1.  Incisors  (or  gnawing  teeth).     These  are  the  front 
teeth.      They  are   long,  and  strong,  curved   teeth,  with 
chisel-shaped,  cutting  edges.      Observe    that  there   is   a 
large  pair  of  incisors  above,  and  another  pair  below,  and 
a  pair  of  very  small  supplementary  incisors  situated  just 
behind  the  large  pair  in  the  upper  jaw. 

2.  Molars  (or  grinding  teeth).     These  are  situated  far- 
ther back,  in  the  sides  of  both  jaws,  deeply  imbedded  in 
the  bone.     The  upper  ones  and  lower  ones  meet  by  flat, 
corrugated,  grinding  surfaces,  between  which  the  food  is 
comminuted.     There  are  six  pairs  above,  five  pairs  below. 
Observe  that  the  molars  are  set  obliquely  in  the  jaws. 
Is   there    any  relation  between   their  direction   and  the 
direction  in  which  the  jaws  are  moved  in  chewing?     Note 
the  absence  of  teeth,  from  a  large  space  between  incisors 
and  molars,  in  both  jaws. 

II.  The  Tongue.  —  Continue  the  lateral  cut  backward 
across  the  angle  of  the  mandible,  cutting  through  the 
bone  with  bone  snips  or  with  stout  scissors.  Forcibly 
turn  the  severed  ramus  of  the  mandible  outward,  break- 
ing its  connection  with  its  fellow,  at  the  symphysis,  in 
front.  This  will  expose  the  buccal  cavity  and  the  tongue. 

Study  the  tongue.  Observe  that  it  is  thick  and  mus- 
cular, attached  posteriorly  to  the  floor  of  the  mouth,  and 
produced  anteriorly  to  a  flattened,  tapering  tip.  Ob- 
serve that  the  surface  of  the  free,  anterior  part  is  soft  and 
delicate,  while  that  of  the  posterior  part,  which  rubs 
against  the  i-uof  of  the  mouth,  is  rough  and  firm.  The 
soft  part  is  dotted  over  with  minute  taste  papillse.  On 
either  side  of  the  tongue,  on  its  sloping  edge,  just  oppo- 
site the  last  molar  tooth,  there  is  a  small,  oval  area  (^papilla 


242  VERTEBRATES. 

foliata),  which  is  crossed  by  minute,  oblique,  parallel  lines. 
There  are  some  relatively  large  taste  buds  imbedded  in 
this  part.  Between  the  two  oval  areas  of  opposite  sides, 
and  a  little  farther  back,  there  are  four  large  papillae 
(circumv allate  papillae)  arranged  in  a  posteriorly  convex 
curve,  two  on  either  side  of  the  median  line.  Each  of 
these  papillae  is  surrounded  by  a  circular  groove. 

III.  The  Palate  and  Adjacent  Parts.  —  Study  the  palate. 
It  is  the  narrow,  median  strip  or  area  along  the  roof  of  the 
mouth.     Its  anterior  portion,  which  is  raised  into  trans- 
verse ridges  against  which  the  tongue  rubs,  is  called  the 
hard  palate.     Its  smooth,  soft,  posterior  half  is  called  the 
soft  palate.     It  ends  behind  in  a  free  border. 

Just  behind  the  small  upper  incisors  are  a  pair  of 
minute  pores  opening  into  small  canals  which  extend  up- 
ward, connecting  the  cavities  of  the  nose  and  the  mouth. 

A  pair  of  small  pits  at  the  sides  of  the  soft  palate,  near 
its  hinder  border,  are  the  tonsils. 

The  pharynx  is  the  backward  continuation  of  the  mouth 
beyond  the  soft  palate.  The  nasal  chamber  opens  into  it 
above  the  soft  palate. 

The  JEustachian  tubes,  coming  from  the  ear,  open  on  the 
sides  of  the  posterior  nasal  chamber  within,  about  the 
middle  of  the  soft  palate.  Split  the  soft  palate  longi- 
tudinally, turn  apart  the  severed  edges,  and  find  the  two 
openings. 

IV.  The  Salivary  Glands.  —  Find  the  salivary  glands. 
They  are  four  pairs  of  large,  pinkish,  reddish,  or  whitish, 
lobulate  bodies  which  secrete  saliva,  and  pour  it  into  the 
mouth  through  small  salivary  ducts :  — 

1.  The  parotid  gland  is  the  largest.  It  lies  in  front  of, 
and  just  below,  the  external  auditory  canal.  Its  duct 
runs  forward  at  first,  just  beneath  the  skin,  and  opens  on 
the  inside  of  the  cheek,  opposite  the  second  upper  molar 
tooth. 


THE   RABBIT.  248 

2.  The  infraorbital  gland  lies  just  below,  and  in  front 
of,  the  eye,  partly  within  the  lower  border  of  the  orbital 
space.     Its  duct  descends  to  open  near  the  duct  from  the 
parotid. 

3.  The  submaxillary  gland  lies  close  to  its  fellow  of  the 
opposite  side,  between  the  angles  of  the  lower  jaw.     Its 
duct  extends  forward,  and  opens  on  the  floor  of  the  mouth, 
about  halfway  between  the  base  of   the  tongue  and  the 
lower  incisors,  and  quite  near  the  median  line. 

4.  The  sublingual  gland  is  a  small,  elongated,  flat  gland, 
lying  close  to  the  inner  side  of  the  mandible,  anterior  to 
the  base  of  the  tongue.     Its  very  minute  duct  opens  also 
on  the  floor  of  the  mouth. 

V.  Hyoid   Bone  and    Glottis.  —  The    hyoid    lone    lies 
deeply  imbedded  in  the  flesh  between  the  angles  of  the 
lower    jaw.       It    furnishes     important    attachments    for 
muscles  of  the  neck.      Its  position  may  be   determined 
by  feeling  with  the  fingers. 

The  pharynx  is  narrowed  posteriorly  into  the  esophagus. 
On  its  floor,  near  the  commencement  of  the  esophagus,  is 
the  opening  of  the  glottis  (or  larynx).  The  glottis  stands 
widely  open,  and  its  entrance  is  guarded  by  an  erect  flap 
of  cartilage,  the  epiglottis.  When  food  is  swallowed,  the 
epiglottis  is  depressed,  and  forms  a  bridge  over  the  glottis, 
across  which  the  food  slides  safely  into  the  esophagus. 
Depress  the  epiglottis,  and  study  its  action. 

VI.  Thorax    and    Abdomen.  —  Extend    the    hind    legs 
backward,  and   the  fore  legs  forward,  and  fasten  them 
so  with  a  tack  through  each  foot.     Observe  two  fairly 
well  defined  regions  in  the  body  of    the  rabbit :   (1)  a 
thorax  with    its   walls    supported   by   ribs,   and    (2)    an 
abdomen  with   soft,    thin,   muscular   walls.      Divide  the 
skin  along  the  median  ventral  line  for  the  entire  length 
of  the  body,  and   strip   it   back,   away  from   the    sides. 
Cut   away  the   ventral   muscular  wall   of   the  abdomen. 


VERTEBRATES, 

Make  a  longitudinal  lateral  cut  through  the  middle  of  the 
ribs,  and  remove  the  ventral  wall  of  the  thorax,  dissecting 
it  carefully  away  from  its  attachments  to  the  internal 
organs. 

The  diaphragm  is  the  transverse  muscular  partition 
found  attached  to  the  posterior  borders  of  the  ribs.  It  is 
the  boundary  between  thorax  and  abdomen.  Lift  up  its 
severed  ventral  margin,  and  note  its  shape,  convex  toward 
the  thorax,  and  concave  toward  the  abdomen.  Observe  a 
thin  tendon  at  its  center.  The  muscular  libers  composing 
it  arise  from  the  walls  of  the  body  cavity,  and  converge 
toward  their  insertion  into  this  central  tendon.  When 
these  contract,  they  draw  the  tendon  posteriorly,  increas- 
ing the  capacity  of  the  thorax. 

Internal  Features.  —  The  large,  dark-colored  liver  lies 
close  against  the  posterior  side  of  the  diaphragm.  The 
capacious  stomach  lies  partly  concealed  by  the  liver,  and 
posteriorly  nearly  the  entire  cavity  of  the  abdomen  is 
filled  with  intestine,  slung  from  the  dorsal  side  of  the 
cavity  in  folds  of  the  mesentery. 

The  pink  lungs,  lying  free  in  the  thoracic  cavity,  rest 
against  the  anterior  surface  of  the  diaphragm.  The  heart, 
within  its  pericardium,  lies  between  the  lungs,  its  apex 
normally  resting  upon  the  diaphragm. 

Note  the  following  parallelisms  in  the  linings  of  thoracic 
and  abdominal  cavities.  The  abdomen  is  lined  with  a 
thin,  transparent,  and  closely  adherent  membrane  (the 
peritoneum),  which,  on  the  dorsal  side,  is  reflected  ventrally 
in  a  double  fold  (the  mesentery)  enveloping  the  viscera. 
The  thoracic  cavity  is  lined  with  a  similar  membrane  (the 
pleura),  which  is  also  reflected  ventrally  from  the  dorsal 
side  to  form  a  double  fold  (the  mediastinum),  which,  at  the 
base  of  each  lung,  is  reflected  completely  over  it,  so  as  to 
inclose  it  as  within  a  bag.  Between  the  two  lungs  there 


THE   RABBIT.  245 

is  thus  left  a  mediastinal  cavity,  within  which  the  heart 
and  its  pericardium  lie.  The  pleura  lining  the  thorax 
and  covering  the  lung  may  be  readily  seen  when  lifted 
with  a  needle  point. 

The  Digestive  System. — The  organs  of  digestion  have 
been  noted  as  far  as  the  esophagus.  The  esophagus  de- 
scends straight  through  the  thorax,  perforating  the  dia- 
phragm, and  entering  the  stomach  on  its  concave  anterior 
border.  Note  the  shape  and  size  of  the  stomach,  the  point 
at  which  the  esophagus  meets  it,  and  the  point  at  which  the 
intestine  springs  from  it.  At  the  origin  of  the  intestine 
is  the  pylorus,  an  internal  valvular  fold  which  guards  the 
passage,  and  prevents  the  premature  exit  of  the  food.  The 
first  part  of  the  intestine  is  the  duodenum,  a  narrow  por- 
tion extended  along  the  right  side  of  the  abdominal  cavity, 
and  folded  upon  itself,  to  form  a  long,  narrow  loop.  Into 
this  part  the  ducts  from  the  gall  bladder  and  the  pancreas 
open.  The  gall  bladder  is  situated  under  one  of  the  five 
lobes  of  the  liver,  and  is  of  a  dark-bluish  color.  Its  duct 
(usually  appearing  brownish  in  color)  extends  posteriorly 
to  open  into  the  duodenum,  not  far  from  the  pylorus. 
The  duct  is  about  an  inch  and  a  half  long.  It  may  be 
made  very  plain  by  squeezing  the  contents  of  the  gall 
bladder  out  into  it. 

The  pancreas  is  whitish  in  color,  and  diffuse  in  form. 
It  is  a  loosely  aggregated  mass,  completely  surrounded  by 
the  duodenal  loop.  Its  short  white  duct  opens  near  the 
middle  of  the  distal  half  of  the  duodenum. 

The  small  intestine  is  the  long  posterior  continuation  of 
the  duodenum.  It  is  of  about  uniform  diameter,  and  is 
looped  up  in  numerous  folds  of  the  mesentery. 

The  ccecum  is  the  long  lateral  pouch  into  the  end  of 
which  the  intestine  opens.  It  is  the  most  conspicuous 
part  of  the  digestive  tract,  on  account  of  its  ventral  posi- 


246  VERTEBRATES. 

tion  and  its  great  size.  It  is  a  sort  of  food  reservoir, 
It  ends  blindly  in  a  narrow,  thick-walled,  finger-shaped 
process  (the  vermiform  appendage). 

The  large  intestine  completes  the  alimentary  canal.  It 
is  distinctly  sacculated  at  its  anterior  end,  becoming 
smooth  posteriorly. 

These  organs  can  be  freely  examined  in  place.  Their 
attachments  should  not  be  severed  until  after  the  blood 
vessels  have  been  studied. 

The  spleen  is  a  dark-red  body  lying  behind  the  stomach, 
and  attached  to  its  left  end. 

Renal  Excretory  System.  —  A  pair  of  compact,  brown- 
ish, bean-shaped  kidneys  lie  closely  attached  to  the  dorsal 
wall  of  the  abdominal  cavity.  Notice  that  the  right  one 
is  anterior  to  its  fellow.  Observe  a  large  artery  entering, 
and  a  large  vein  leaving,  each  kidney.  Observe  also  a 
long  white  duct  (a  ureter)  extending  posteriorly  from 
each  kidney,  to  open  into  the  urinary  bladder,  a  whitish 
membranous  sac  lying  ventral  to  the  posterior  end  of  the 
large  intestine.  Associated  with  the  afferent  duct  of  the 
bladder  are  the  passages  from  the  reproductive  organs; 
and  the  external  aperture  for  these  is  separate  from  the 
anal  aperture. 

The  Circulatory  System  is  very  similar  to  that  of  a  bird. 
The  heart  is  four-chambered,  consisting  of  right  and  left 
auricles  and  ventricles.  The  boundaries  of  these  cham- 
bers are  evident  from  the  outside  ;  but  the  heart  should  be 
dissected  later,  to  show  the  relative  thickness  of  the  walls 
of  these  chambers,  and  the  valves,  which  prevent  the 
return  of  blood  at  the  entrance  to  the  ventricles  and  to 
the  aorta. 

I.  The  Venous  System.  —  The  blood  is  brought  to  the 
heart  through  right  and  left  prcecavce  and  the  single 
large  postcava.  These  three  vessels  enter  the  right 


THE    RABBIT.  247 

auricle.  The  principal  branches  of  each  prgecava  are 
three  :  (1)  a  jugular  vein  coming  from  the  head  ;  (2) 
a  subclavian  vein  coming  from  the  shoulder  and  fore 
limb  ;  and  (3)  a  mammary  vein  coming  from  the  ventral 
wall  of  the  thorax.  The  principal  branches  of  the 
postcava  are  the  short,  wide  hepatic  veins  entering  it  in 
the  liver,  the  renal  veins  coming  from  the  kidneys,  the 
spermatic  (or  ovarian)  veins  (according  to  sex)  coming 
from  the  reproductive  organs,  and  the  large  external  iliac 
veins  coming  from  the  hind  limbs.  The  last-named  are 
called  femoral  veins  posterior  to  the  abdominal  cavity. 

Another  set  of  veins,  constituting  the  portal  system,  col- 
lects the  blood  from  the  digestive  organs  of  the  abdominal 
cavity,  and  carries  it  through  the  portal  vein  to  the  liver. 
This  blood  percolates  through  the  substance  of  the  liver 
before  being  collected  again  into  the  hepatic  veins. 

II.  The  Pulmonary  System.  —  The  blood  collected  into 
the  right  auricle  descends,  through  an  opening  guarded 
by  a  valve,  into  the  right  ventricle,  whence  it  is  expelled 
to  the  lungs  through  the  pulmonary  arteries.     These  arise 
together  from  the  anterior  border  of  the  ventral  surface 
of  the  auricle,  and,  arching  about  the  left  auricle,  separate, 
and  go  direct  to  the  lungs.     After  distribution  through 
the  capillaries  in  the  walls  of  the  air  cells  of  the  lungs, 
the   blood   is   collected   into   the   pulmonary   veins,    and 
returned  directly  to   the  left   auricle.       The   pulmonary 
artery  and  vein  and  connecting  capillaries  constitute  the 
pulmonary  system.     The  obvious  purpose  of  this  part  of 
the  circulatory  system  is  the  aeration  of  the  blood. 

III.  The  Arterial  System.  —  From  the  left  auricle  the 
blood   descends,  through  an  orifice  guarded  by  a  valve, 
into  the  left  ventricle,  whence  it  is  expelled  through  the 
aorta.    The  aorta  curves  dorsally  and  toward  the  left  side 
of  the  body,  and  then   extends   posteriorly  beneath   the 
dorsal   wall   and   above  the  viscera.      It   gives  off  ante- 


248  VERTEBRATES. 

riorly  near  its  origin  a  large  innominate  artery,  and  a 
little  farther  out  from  the  heart  a  smaller  left  subdavian 
artery,  which  goes  to  the  left  shoulder,  and  thence  to  the 
fore  limb.  A  branch  of  the  subclavian,  which  runs  along 
the  inner  side  of  the  ventral  wall  of  the  thorax,  is  the 
mammary  artery.  The  innominate  artery  soon  divides 
off  a  left  carotid  artery,  and  then  bifurcates  into  right 
carotid  and  right  subclavian  arteries. 

That  part  of  the  aorta  which  extends  posteriorly  beyond 
the  arch  is  called  the  dorsal  aorta.  It  gives  off  in  the 
thorax  a  series  of  small  intercostal  arteries,  which  extend 
laterally  along  the  inner  walls  of  the  thorax,  one  behind 
each  rib.  Its  principal  branches  in  the  abdomen  are  three 
single  arteries,  which  pass  ventrally  through  the  mesentery 
to  the  digestive  organs,  and  three  paired  arteries. 

The  foremost  of  the  single  arteries  (the  cceliac  artery) 
arises  close  behind  the  diaphragm,  and  its  branches  are 
distributed  to  the  liver,  stomach,  and  spleen  ;  the  second 
(the  anterior  mesenteric  artery)  arises  a  short  distance  be- 
hind the  first.  Its  branches  supply  the  greater  part  of 
the  intestine.  The  third  (the  posterior  mesenteric  artery) 
is  small.  It  arises  toward  the  posterior  end  of  the  abdomi- 
nal cavity.  Its  branches  are  distributed  to  the  hinder 
end  of  the  intestine. 

Of  the  paired  arteries,  the  foremost  are  the  large  renal 
arteries,  which  go  to  the  kidneys.  The  second  are  the 
very  small  spermatic  (or  ovarian)  arteries,  which  go  to 
the  reproductive  organs.  %  The  hindmost  are  the  very 
large  common  iliac  arteries,  into  which  the  dorsal  aorta 
seems  to  divide.  Posterior  to  the  body  cavity,  these  are 
called  femoral  arteries.  Between  the  spermatic  and  com- 
mon iliac  arteries,  several  small  lumbar  arteries  arise  on 
the  dorsal  side  of  the  aorta,  to  be  distributed  right  and 
left  to  the  dorsal  abdominal  wall,  and  to  the  thick  muscles 
of  the  back. 


THE    RABBIT.  249 

It  should  be  noted  that  the  venous  and  arterial  systems 
roughly  correspond  to  each  other  in  the  distribution  of 
their  parts. 

The  Respiratory  System.  —  That  the  lungs  are  envel- 
oped in  the  pleura,  that  they  are  attached  at  their  ante- 
rior end,  and  float  freely  behind,  within  the  thoracic 
cavity,  have  already  been  noted.  That  they  communicate 
anteriorly  with  a  pair  of  bronchi,  which  unite  into  the 
trachea,  will  have  been  noticed  in  the  dissection  of  the 
blood  vessels.  How  many  lobes  are  there  in  the  right 
lung  ?  In  the  left  ? 

Observe  that  bronchi  and  trachea  are  made  up  of  a 
series  of  cartilaginous  rings.  On  which  side  of  the  trachea 
are  these  rings  thickest,  and  why  ?  Note  the  absence  of 
any  distinguishable  syrinx  at  the  division  of  the  trachea 
into  bronchi.  The  voice  organ  in  the  rabbit  is  the 
larynx,  developed  at  the  anterior  end  of  the  trachea. 
The  epiglottis  stands  at  its  anterior  ventral  border.  It 
is  slightly  wider  and  firmer  than  other  parts  of  the 
trachea.  Dissect  the  larynx  free  from  all  its  lateral 
attachments,  and  observe  that  it  is  composed  chiefly  of 
two  rings  of  cartilage.  The  anterior  one  is  wide  in  front, 
but  incomplete  dorsally.  It  is  called  the  thyroid  cartilage. 
The  posterior  one  is  a  complete  ring,  wider  on  its  dorsal 
side.  It  is  called  the  cricoid  cartilage. 

Make  a  median  ventral  slit  down  the  larynx,  and  draw 
apart  the  severed  edges.  Observe  the  thin  sheets  of 
muscle  and  connective  tissue  which  bind  the  cartilages 
together.  Two  little  nodules  of  cartilage  within  the 
larynx,  and  on  the  dorsal  side,  are  the  arytenoids. 

The  two  shallow,  lateral  depressions  on  the  inner  side 
of  the  walls  of  the  larynx  are  the  ventricles.  The  pair  of 
delicate  folds  which  form  the  posterior  boundaries  of  the 
ventricles  are  the  vocal  cords.  These  are  folds  of  the 


250  VERTEBRATES. 

mucous  membrane,  or  inside  skin  (which  lines  all  the  cavi- 
ties  of  the  body  that  have  open  communication  with  the 
exterior),  strengthened  by  slender  elastic  ligaments.  They 
are  attached  posteriorly  to  the  arytenoids,  by  rotation  of 
which  they  are  stretched  across  the  tube  of  the  larynx. 
When  fully  stretched,  the  opening  between  them  is  but 
a  narrow  vertical  cleft.  In  this  position  they  vibrate 
readily  in  a  passing  current  of  air  expelled  from  the  lungs, 
and  they  thus  produce  voice.  A  pair  of  folds  of  similar 
appearance,  at  the  anterior  boundaries  of  the  ventricles, 
are  the  false  vocal  cords. 

The  Lacteal  System.  —  The  thoracic  duct  is  a  slender, 
thin- walled  tube  which  extends  through  the  thorax  length- 
wise, close  to,  but  a  little  above,  the  dorsal  aorta.  It  is 
formed  by  the  union  of  numerous  small  vessels,  called 
lacteals,  in  the  anterior  part  of  the  mesentery,  in  the 
abdominal  cavity.  It  perforates  the  diaphragm,  and 
passes  directly  forward  to  the  anterior  end  of  the  thoracic 
cavity,  where  it  widens  somewhat,  and  turns  inward,  to 
open  into  the  left  preecava,  near  to  its  subclavian  branch. 
It  receives  in  its  course  other  lymphatic  vessels  from 
nearly  all  parts  of  the  body.  These  vessels  form  a  sort 
of  drainage  system  for  the  tissues.  The  lymph  they 
bring,  and  the  liquid  products  of  digestion  brought  by 
the  lacteals  from  the  intestine,  are  carried  by  the  thoracic 
duct,  and  emptied  into  the  venous  system,  to  mix  and 
commingle  with  the  blood. 

The  pale,  soft,  glandular-appearing  body,  through  which 
the  curved  anterior  end  of  the  thoracic  duct  passes  before 
entering  the  prsecava,  is  the  thymus. 

Spinal  and  Sympathetic  Nerves.  —  The  spinal  nerves 
may  be  seen  through  pleura  and  peritoneum,  in  the  dorsal 
wall  of  the  body  cavity. 

A  double  chain  of  sympathetic  ganglia  extends  along 


THE    RABBIT.  251 

close  beside,  and  ventral  to,  the  spinal  column.  The 
ganglia  are  connected  with  one  another,  and  with  the  roots 
of  the  spinal  nerves,  by  commissural  nerves.  These  are 
very  difficult  of  dissection. 

Removal  of  the  Brain.  —  Cut  away  the  top  of  the  cra- 
nium, and  expose  the  brain  fully.  The  elongate  oval 
olfactory  lobes  at  its  anterior  end  will  be  conspicuous. 
Cut  these  off  as  far  forward  as  possible,  and  gently  lift  the 
brain  out  of  the  cranial  cavity,  on  a  thin,  narrow  blade  of 
metal,  watching  closely,  and  severing  the  roots  of  the 
cranial  nerves  as  fast  as  they  appear,  leaving  as  great  a 
portion  of  each  as  possible  attached  to  the  brain.  Twelve 
pairs  of  cranial  nerves  should  be  found  during  this  oper- 
ation. Proceeding  from  the  front,  these  are  :  — 

1.  The  olfactory  nerves,  the  roots  of  which  were   cut 
off   at   the   anterior   end   of   the   olfactory  lobes   of  the 
brain. 

2.  The    optic  nerves,  large   and   conspicuous,    at   first 
diverging  but  little,  as  they  extend  forward  from  their 
point  of  crossing  on  the  median  ventral  line. 

3.  Two  pairs  of  slender  nerves,  Appearing  behind  the 
crossing  of  the  optic  nerves. 

4.  The  trigeminal  nerves,  very  large  and  conspicuous, 
arising  a  little  farther  back,  and  a  little  more  remote  from 
the  median  ventral  line. 

5.  Two  pairs  of  slender  nerves,  close  behind  the  tri- 
geminal, the  anterior  pair  somewhat  nearer  the  median 
line. 

6.  The    auditory  nerves,  which   are   large,  and   which 
arise  a  short  distance  behind  the  trigeminal,  but  farther 
from  the  median  line. 

7.  Two  pairs  of  rather  small  nerves,  which  arise  close 
behind,  and   a   little   above,  the   auditory   nerves.     The 
larger  pair  of  these  are  the  vagus  nerves. 


252  VERTEBRATES. 

8.  Two  pairs,  which  arise,  by  many  slender  rootlets, 
from  the  ventral  surface  of  the  hindmost  part  of  the 
brain,  rootlets  of  one  pair  in  part  from  the  anterior  end 
of  the  spinal  cord. 

Parts  of  the  Brain.  —  Cut  off  the  spinal  cord,  and  place 
the  brain  in  a  little  alcohol,  for  a  superficial  examination 
of  its  parts.  On  the  dorsal  side,  note  the  large,  smooth, 
cerebral  hemispheres  immediately  behind  the  olfactory  lobes, 
and  in  the  posterior  angle  between  them,  011  the  median 
line,  the  pineal  body.  Posterior  to  the  hemispheres,  the 
cerebellum  covers  the  greater  part  of  the  dorsal  surface. 
It  is  made  up  of  a  large,  transversely  ridged,  central  lobe; 
a  pair  of  oblique,  lateral  lobes;  and,  on  its  outer  edges,  a 
pair  of  small,  rounded,  floccular  lobes.  The  dorsal  sur- 
face of  the  medulla  appears  behind  the  central  lobe  of  the 
cerebellum. 

On  the  ventral  surface  observe  the  olfactory  lobes, 
extending  backward,  beneath  the  anterior  end  of  the 
hemispheres.  Observe  that  a  large,  oval,  temporal  lobe  is 
marked  off  on  the  ventral  surface  by  a  shallow  groove 
from  the  remainder „  of  each  hemisphere.  Observe  the 
crossing  of  the  optic  nerves.  They  may  be  traced  out- 
ward and  backward  to  the  concealed  optic  lobes  by  turn- 
ing the  temporal  lobes  of  the  hemispheres  aside.  Close 
behind  the  crossing  of  the  optic  nerves  find  a  narrow 
median  slit,  the  aperture  of  the  infundibulum,  leading 
down  into  the  pituitary  body,  which  was  probably  left  be- 
hind in  the  base  of  the  cranium  when  the  brain  was 
removed.  The  floccular  and  lateral  lobes  of  the  cerebel- 
lum are  visible  on  either  side,  and  these  are  connected 
across  the  ventral  surface  by  a  stout  band  of  nerve  fibers. 
The  medulla,  tapering  posteriorly,  and  studded  with  nu- 
merous nerve  roots,  forms  the  remaining  posterior  part  of 
the  ventral  surface. 


THE   RABBIT.  253 

The  Skeleton.  —  The  axial  part  consists  of  the  spinal 
column  (composed  of  vertebrce)  and  of  the  skull.  The 
bones  of  the  whole  axial  series  are  perforated,  and  so 
placed  together,  end  to  end,  as  to  form  a  canal,  which 
lodges  and  protects  the  central  parts  of  the  nervous  sys- 
tem, —  brain  and  spinal  cord.  The  vertebral  series  also 
forms  a  very  strong  yet  flexible  support  for  all  other 
parts  of  the  body. 

I.  Vertebrae  and  Ribs.  —  The  vertebra  may  be  con- 
sidered as  forming  five  groups  :  (1)  cervical  (or  neck) 
vertebrce;  (2)  thoracic  (or  chest)  vertebrce,  which  bear 
movably  articulated  ribs  ;  (3)  lumbar  (or  back)  vertebrce, 
without  ribs,  the  largest  of  the  series  ;  (4)  sacral  verte- 
brce, which  are  fused  together,  and  support  the  bones  of 
the  pelvis ;  and  (5)  caudal  (or  tail)  vertebrce.  How  many 
vertebrae  are  there  in  each  of  these  five  groups  ? 

Examine  one  of  the  middle  lumbar  vertebrae  as  a  type, 
and  in  it  find  the  usual  parts,  —  centrum,  neural  arch,  neural 
spine,  transverse  processes,  and  articular  processes.  Find 
also  a  median  ventral  process  (hypapophysis)  projecting 
downward  directly  from  the  centrum.  A  pair  of  flat 
plates  of  bone  (epiphyses)  may  be  found  applied  to  the 
ends  of  the  centrum,  if  the  vertebra  be  that  of  a  young 
animal.  These  become  anchylosed  with  the  centrum 
with  age. 

The  transverse  processes  of  the  cervical  vertebrae  are 
broad  and  flat  and  perforated,  and  the  series  of  perfora- 
tions forms  an  imperfect  canal  for  the  passage  of  a  nerve 
and  an  artery.  The  parts  of  the  transverse  processes  out- 
side the  perforations  are  homologous  with  the  ribs  of  the 
vertebrae  farther  back. 

Note  that  each  distinguishable  rib  has  two  articulations 
with  its  vertebra,  —  a  head,  which  meets  the  centrum  ;  and 
a  tubercle,  which  meets  the  transverse  process.  The  space 
inclosed  between  these  two  articulations  corresponds 


254  VERTEBRATES. 

roughly  to  the  perforation  in  the  transverse  process  of 
the  cervical  vertebra.  Examine  one  of  the  ribs  near  the 
middle  of  the  series,  and  note  its  shape,  position,  and 
range  of  movability.  Note  that  it  has  a  sternal  as  well 
as  a  vertebral  portion,  and  note  that  the  sternal  portion 
is  more  or  less  cartilaginous.  Note  that  the  central  part 
of  the  sternum,  to  which  the  ribs  attach  at  their  distal 
end,  is  transversely  segmented.  Observe  that  the  fore- 
most segment  (the  manubrium)  is  large,  and  is  produced 
anteriorly  in  a  prominent  keel.  Observe  that  the  hind- 
most segment  (the  xiphisternum)  is  a  slender  rod  of 
bone,  supporting  a  broad,  flat  cartilage.  Which  ribs  are 
shortest  ?  Which  longest  ?  Which  have  no  sternal  por- 
tion ?  Which  have  but  one  articulation  with  their  corre- 
sponding vertebrae  ?  Which  articulate  partially  with  other 
than  their  own  vertebras  ? 

Note  the  decrease  in  size  of  the  vertebrae  posterior  to 
the  first  sacral,  and  the  gradual  disappearance  of  all  the 
processes. 

II.  Atlas  and  Axis.  —  The  first  and  second  cervical 
vertebrae  show  special  adaptive  modifications,  and  have 
received  special  names.  The  first  is  the  atlas.  It  bears 
the  skull  upon  two  concave,  articular  surfaces,  which 
meet  the  occipital  condyles  of  the  skull.  It  has  no 
centrum  ;  or,  rather,  its  centrum  is  probably  the  odontoid 
process  of  the  second  vertebra.  A  transverse  ligament 
divides  the  very  large  perforation ;  and  the  division  of 
it  anterior  to  the  ligament  is  occupied  by  this  odontoid 
process,  around  which  the  atlas  rotates.  The  spinal  cord 
occupies  the  space  posterior  to  the  ligament. 

The  second  vertebra  is  the  axis.  It  has  a  broad,  flat 
centrum,  produced  anteriorly  into  the  conical  odontoid 
process.  A  suture  between  this  process  and  the  centrum 
is  readily  seen  in  young  rabbits,  and  indicates  that  the 
process  has  become  attached  to  the  second  vertebra,  while 


THE   RABBIT. 


255 


its  position  indicates  that  it  may  have  belonged  originally 
to  the  first. 

Study  the  action  of  atlas  and  axis,  and  note  that  the 
head  can  be  nodded  backward  and  forward  on  -the  atlas, 
but  that,  in  its  rotation,  the  atlas  turns  round  the  odon- 
toid process  of  the  axis. 

III.  The  Skull.  —  In  the  skull,  note  again  the  direction 
of  the  teeth  and  their  position  in  the  jaws.  Note  the 
articulation  of  the  lower 
jaw  or  mandible  with 
the  remainder  of  the 
skull.  Observe  the  two 
rounded  occipital  con- 
dyles  beside  the  foramen 
magnum.  Observe  that 
the  orbits  communicate 
through  the  interorbital 
foramen.  Note  that  the 
bones  of  the  top  of  the 

cranium  meet  each  other  SKULL  OF  RABBIT  (gide 

by  jagged  sutures. 

The  following  bones  should  be  readily  distinguishable 
in  an  adult  skull.  The  occipital  forms  a  complete  bony 
ring  around  the  foramen  magnum.  It  is  formed  origi- 
nally of  a  number  of  separate  occipital  bones.  Proceed- 
ing forward  on  the  dorsal  surface,  a  small  median  inter- 
parietal  bone  will  be  found  fitted  in  between  the  front  of 
the  occipital  and  the  posterior  angle  between  the  two 
parietals,  which  meet  by  a  median  suture  directly  in  front. 
The  parietals  form  the  greater  part  of  the  roof  of  the 
cranial  cavity.  Anterior  to  the  parietals,  a  pair  of  large 
frontals  complete  the  roof  of  the  cranium  in  front,  and 
send  out  a  large  crescentic  process  above  each  orbit,  and 
form  the  dorsal  third  of  the  orbital  wall.  The  frontals 
meet  by  a  median  dorsal  suture.  Anterior  to  the  fron- 


256 


VERTEBRATES. 


tals,  two  long,  narrow  nasals  complete  the  median  dorsal 
surface,  and  form  the  bony  support  of  the  snout.  The 
two  stout  bones  which  carry  the  upper  incisors,  and 
which  are  situated  beneath  the  nasals,  and  meet  on  the 
median  line  in  front,  are  the  premaxillaries.  Behind 
them  are  the  maxillaries,  large  and  irregular,  forming 
the  greater  part  of  the  skeleton  of  the  upper  jaw.  Ven- 
trally  they  bear  the  upper  molars ;  and  each  sends  out  a 
stout  lateral  process,  which  forms  part  of  the  anterior 

boundary  of  the  orbit. 
The  nasal  cavity 
lies  beneath  the  na- 
sals and  above  the 
maxillaries  and  pre- 
maxillaries. Looking 
into  it  from  the  front, 
a  number  of  thin, 
irregular  plates  of 
bone  (the  turbinals) 
will  be  seen.  The 
anterior  of  these,  the 
more  delicate  and 

SKULL  OF  RABBIT  (dorsal  and  ventral  views  of    complex  jn  structure, 
cranium). 

are    developed    from 

the  maxillaries,  and  are  called  the  maxillo-turbinals.  The 
posterior  are  developed  from  the  (concealed)  ethmoid, 
and  are  called  ethmoturbinals.  The  ethmoid  terminates 
posteriorly  in  a  transverse  cribriform  plate,  set  in  the  an- 
terior end  of  the  cranial  cavity.  This  plate  may  be  seen 
in  a  skull  from  which  the  roof  of  the  cranial  cavity  has 
been  removed.  It  is  perforated  for  the  passage  of  the 
branches  of  the  olfactory  nerves  to  the  nose.  Within 
the  nasal  cavity,  the  terminations  of  these  nerves  are  dis- 
tributed through  the  mucous  membrane,  which  covers  the 
turbinal  bones.  The  great  extent  of  surface  over  which 


THE   RABBIT.  257 

nerve  endings  can  come  into  contact  with  the  air  corre- 
sponds with  the  keen  sense  of  smell  possessed  by  the 
rabbit. 

The  lachrymal  bone  of  each  side  forms  a  large  part  of 
the  anterior  wall  of  the  orbit,  and  joins  the  frontal  by  a 
suture  above. 

The  squamosal  bones  form  the  greater  part  of  the  con- 
vex lateral  walls  of  the  cranial  cavity,  and  send  out  a 
stout  lateral  process  to  form  part  of  the  posterior  border 
of  the  orbit.  The  flattened  bars  of  bone  which  connect 
this  process  of  the  squamosal  with  the  corresponding 
backward  process  from  the  maxillary,  and  complete  the 
outer  border  of  the  orbits,  are  the  molars  (or  cheek  bones). 

Two  (composite)  bones  remain  to  be  found  on  the 
median  ventral  surface  of  the  cranium.  These  are  the 
basisphenoid,  which  has  a  triangular  body  (seen  from 
below)  and  two  flattened,  wing-shaped,  lateral  processes, 
and  which  is  situated  immediately  in  front  of  the  occip- 
ital ;  and  the  presphenoid,  a  narrow  bone  in  front  of  the 
basisphenoid,  extended  upward  into  a  thin  median  plate 
between  the  orbits,  and  perforated  by  the  interorbital 
foramen. 

The  pterygoids  are  two  narrow,  vertical  plates  of  bone, 
attached  to  the  base  of  the  skull  at  the  lateral  junction 
of  the  two  sphenoids.  Each  has  a  free  posterior  border, 
which  ends  below  in  a  curved  process. 

The  palatines  are  two  nearly  vertical  plates  of  bone, 
which  extend  forward  from  the  pterygoids,  form  the 
lateral  walls  of  the  posterior  nasal  opening,  and  meet  each 
other  on  the  median  line  of  the  roof  of  the  mouth  by 
horizontal  platelike  processes. 

IV.  Shoulder  Girdle  and  Arm  Bones.  —  In  the  shoulder 
girdle  the  three  usual  bones  of  each  side  may  not  be  at 
first  recognizable.  The  scapula  is  a  large,  flat,  triangular 
bone,  expanded  at  the  end  which  forms  the  apex  of  the 

NEED.  ZOOL.  — 17 


258  VERTEBRATES. 

triangle,  and  hollowed  there  to  form  a.  cavity,  into  which 
the  head  of  the  humerus  fits.  The  coracoid  is  not  a  sepa- 
rate bone  in  the  adult  rabbit,  but  only  a  curved  process 
attached  to  the  scapula,  and  overhanging  the  head  of  the 
humerus.  The  clavicle  is  a  slender,  incomplete  bone, 
developed  within  a  ligament  which  extends  from  the 
sternum  to  the  scapula. 

The  bones  of  the  fore  limb  are  humerus,  radius,  ulna, 
carpal  and  metacarpal  bones,  and  phalanges.  All  these 
are  easily  recognizable.  The  humerus  is  the  single  bone 
of  the  upper  arm.  The  ulna  is  the  larger  of  the  two 
bones  of  the  forearm.  Its  enlarged  proximal  end  bears 
the  olecranon  process,  which  forms  the  angle  at  the  elbow. 
Both  radius  and  ulna  have  a  thick  cap  or  transverse  plate 
of  bone  (epiphysis)  more  or  less  completely  coossified 
with  the  shaft  of  the  bone.  The  small  carpal  bones  are 
arranged  in  two  transverse  TOAVS,  —  three  bones  in  the 
proximal  row,  and  four  in  the  distal  row,  —  with  a  single 
minute,  roundish  bone  between  the  rows,  on  the  median 
line.  The  metacarpals  are  a  transverse  series  of  elongated 
bones  (the  inner  one  short) ;  and  the  phalanges  (or  finger 
bones)  are  two  in  the  inner  digit  or  thumb,  and  three  in 
each  of  the  other  digits. 

V.  Pelvic  Girdle  and  Leg  Bones.  —  In  the  pelvic  girdle 
the  usual  three  bones  of  each  side  are,  as  usual,  fused  with 
each  other,  and  firmly  attached  to  the  sacral  vertebra. 
The  two  sides  of  the  girdle  are  united  also  in  a  ventral 
symphysis.  Each  of  the  three  takes  part  in  the  formation 
of  the  deep  cup-shaped  acetabulum,  in  the  sides  of  which 
the  boundaries  between  them  may  readily  be  seen  in 
young  specimens.  The  ilium  forms  the  anterior  part  of 
the  girdle  on  each  side.  It  is  broadly  flattened  in  front, 
narrowed  behind,  and  it  forms  about  half  of  the  acetab- 
ulum. The  ischium  is  posterior  and  dorsal,  and  forms 
about  one  third  of  the  acetabulum.  Its  posterior  portion 


THE   RABBIT.  259 

is  flattened  and  thickened  at  the  margin,  to  form  the 
tuber osity  of  the  ischium.  The  pubis  is  ventral.  It  is 
separated  in  part  from  the  ischium  by  the  large,  oval 
obturator  foramen  ;  but  the  ventral  symphysis,  uniting  the 
two  halves  of  the  pelvic  girdle,  is  formed  of  both  ischium 
and  pubis  on  each  side,  and  the  boundary  line  between 
them  is  not  discoverable  except  in  very  young  speci- 
mens. 

The  bones  of  the  hind  limb  are  femur,  tibia,  fibula,  tar- 
sal,  metatarsal,  and  phalanges,  and  a  few  small  sesamoid 
bones,  developed  in  the  tendons  at  some  of  the  joints, 
and  not  forming  a  part  of  the  skeleton  proper.  The 
largest  of  these  sesamoid  bones  is  the  patella  (or  knee- 
pan),  developed  in  front  of  the  knee  joint  in  the  tendon 
of  the  extensor  muscles  of  the  leg. 

The  femur  is  the  single  bone  of  the  thigh.  The  large 
bone  of  the  shank  is  the  tibia ;  the  small  one,  distinct  at 
its  proximal  end,  but  fused  with  the  tibia  distally,  is  the 
fibula.  The  tarsus,  like  the  carpus,  consists  of  two  trans- 
ver^se  rows  of  small  bones,  with  a  single  bone  between  the 
two  rowso-  The  proximal  row  consists  of  two  relatively 
large  bones,  the  distal  row  of  three  smaller  ones,  while 
the  single  bone  between  the  rows  is  at  the  inner  side  of 
the  foot.  The  metacarpals  are  a  transverse  series  of  four 
elongated  bones,  and  the  phalanges  are  three  in  each  digit. 
The  first  digit  of  the  foot,  corresponding  to  the  great  toe, 
is  wanting. 

The  rabbit  is  a  representative  of  the  vertebrate  class 
Mammalia  (the  mammals,  or  milk-givers). 

A  cat  or  dog  may  well  be  studied,  as  showing  the  car- 
nivorous type  of  mammalian  structure ;  and  a  bat,  as 
showing  the  adaptation  of  mammalian  structure  to  aerial 
locomotion. 


260  VERTEBRATES. 


THE  LIFE  PROCESS  IN  VERTEBRATES. 

The  life  process  is  essentially  the  same  in  all  animals, 
differing  in  different  animals  only  in  the  means  by  which 
it  is  carried  out.  The  perfection  of  the  means  —  the 
adaptation  of  the  means  to  new  and  higher  conditions 
of  life  —  has  made  the  vertebrates  the  dominant  group 
among  animals. 

I.  Nutrition.  —  The  organs  subservient  to  nutrition  have 
been  grouped  as  organs  (1)  of  digestion,  (2)  of  circulation, 
(3)  of  respiration,  and  (4)  of  excretion;  and  to  these 
might  be  added  (5)  organs  of  prehension,  for  grasping  food, 
and  (6)  organs  of  mastication,  for  chewing  it,  although  the 
organs  of  the  last  two  groups  are  not  exclusively  sub- 
servient to  the  nutritive  function,  and  are  not  present  in 
all  vertebrates. 

1.  Digestion  takes  place  in  the  alimentary  canal,  parts 
of  which  are  specialized  for  the  reduction  of  the  food,  and 
other  parts  for  the  absorption  of  it  when  digested.     Four 
digestive  secretions  are  poured  upon  the  food  normally 
in  its  course,  —  saliva,  from  the  salivary  glands ;  gastric 
juice,  from  glands  in  the  walls  of  the  stomach  ;  bile,  from 
the  gall  bladder  of  the  liver ;  and  pancreatic  juice,  from 
the  pancreas.     The  greater  part  of  the  digested  food  is 
absorbed  through  the  walls  of  the  intestine,  to  be  passed 
into  the  circulation.     In  the  highest  vertebrates  it  is  col- 
lected by  the  lacteals  of  the  mesentery  into  the  thoracic 
duct,  and  poured  thence  directly  into  the  venous  system. 

2.  Circulation  is  effected  through  a  closed  system  of 
blood  vessels,  consisting  of  the  heart,  arteries,  veins,  and 
capillaries.    Through  this  system  the  food  dissolved  in  the 
blood  is  carried  to  every  vascular  part  of  all  the  tissues. 
The  three  types  of  circulation  found  in  the  vertebrates 
studied  are  roughly  outlined  in  the  accompanying  dia- 


THE   LIFE   PROCESS  IN   VERTEBRATES. 


261 


gram.  Their  relation  to  the  digestive,  respiratory,  and 
renal  organs  is  shown  very  diagrammatically. 

3.  Respiration  is  effected  by  means  of  gills  or  of  lungs. 
In  those  vertebrates  which  have  naked,  moist  skins,  it  is 
probable  that  considerable  air  is  absorbed  directly  through 
the  skin. 

When  the  blood  has  been  replenished  and  aerated,  ma- 
terials have  been  supplied  for  all  the  chemical  changes 


Fish  or  Tadpole. 


Adult  Frog. 


Eabbit. 


COMPARATIVE  DIAGRAM  OF  CIRCULATION,  SHOWING  IN  A  GENERAL 

THE  COURSE  AND  DISTRIBUTION  OF  THE  BLOOD  :  V,  ventricle ;  G,  gills  ; 
P,  lungs  and  pulmonary  vessels ;  L,  liver ;  S,  stomach  ;  /,  intestine ; 
K,  kidney.  Black  vessels  carry  venous  blood ;  light  ones,  arterial  blood. 
Arrows  indicate  the  course  of  circulation. 

(metabolism)  which  take  place  in  the  tissues.  The  con- 
structive processes  (anabolism),  by  which  the  food  be- 
comes tissue ;  .and  the  destructive  processes  (katabolism), 
by  which  the  tissue  becomes  waste  water,  carbonic  acid, 
etc., — are,  so  far  as  we  know,  the  same  in  all  animals; 
and  the  end  of  this  building-up  and  tumbling-down  of 
organic  molecules,  in  "continual  round  of  change,"  is  the 
production  of  heat,  motion,  nerve  force,  etc.,  necessary  to 
the  animal's  life  and  activities. 


262  VERTEBRATES. 

4.  Excretion  is  performed  by  the  skin,  the  lungs,  and 
the  kidneys. 

II.  Reproduction.  —  As  in  all  other  animals  except  pro- 
tozoans, reproduction  in  vertebrates  is  by  means  of  eggs. 
The  sexes  are  distinct  in  all,  and  the  eggs  are  fertilized 
either  within  or  without  the  body  of  the  parent.     In  the 
mammals  the  eggs  are  retained  and  developed  within  a 
specialized  part  of  the  oviduct,  the  uterus  (or  womb).    The 
young  are  born  after  their  embryonic  life  is  past,  and  are 
nourished  with  milk  secreted  in  the  mammary  glands  of 
the  female.     Throughout  the  group,  and  throughout  the 
animal  kingdom,  the  decrease  in  the  number  of  progeny 
is  proportionate  with  their  increased  security  from  ene- 
mies during  the  period  of  development. 

III.  Voluntary  Motion.  — An  internal  skeleton,  usually 
of  bone,  furnishes  support  and  points  of  attachment  for 
the  muscles  of  the  vertebrates.     The  muscles  overlie,  and 
more  or  less  completely  envelop,  the  bones.      This  is  a 
radically  different  arrangement  of  skeleton  and  muscle 
from  that  found  in  crustaceans  and  insects.     The  muscle 
fibers  of  vertebrates  are  insheathed  together  in  connective 
tissue,  and  often  inserted  into  tendons,  affording  them 
greater  unity  and  efficacy  of  action. 

The  limbs  of  vertebrates  are  never  more  than  two 
pairs,  and  may  be  entirely  wanting.  They  are  usually 
developed  for  locomotion :  as  fins  for  swimming ;  wings  for 
flying ;  legs  for  walking,  running,  leaping,  etc.  Locomo- 
tion is  aided  in  fishes  by  unpaired  fins,  and  by  the  stout, 
muscular  tail ;  and  in  some  reptiles  (snakes),  by  the  move- 
ment of  the  spinal  column  and  ribs.  Movable  tactile 
organs,  such  as  the  barbels  of  fishes  and  the  "whiskers" 
of  mammals,  are  often  present.  Some  of  the  most  clumsy, 
ungainly,  armor-encumbered  animals,  as  well  as  some  of 
the  fleetest  and  most  graceful  on  land,  in  air,  or  in  water, 
are  found  among  the  vertebrates. 


THE   LIFE   PROCESS   IN   VERTEBRATES.  263 

IV.  Sensation.  — The  position  of  the  central  nervous 
system  (i.e.,  of  the  brain  and  spinal  cord)  in  vertebrates, 
dorsal  to  the  center  of  the  bony  axis  of  the  skeleton,  and 
inclosed  within  a  dorsal,  neural  canal,  is  very  charac- 
teristic of  the  group.  In  the  lowest,  the  brain  is  but 
little  developed  at  the  anterior  end  of  the  spinal  cord; 
but,  as  we  ascend  the  vertebrate  scale,  it  becomes  more 
and  more  highly  specialized.  The  cerebral  hemispheres, 
which  are  the  seat  of  intelligence,  reach  their  relative 
maximum  development  in  man.  The  spinal  and  cranial 
nerves  are  distributed  to  all  the  muscles  of  the  body,  to 
the  skin,  and  certain  of  them  to  the  blood  vessels  and 
to  the  internal  organs  ;  and  all  these  parts  are  thus  placed 
in  communication  with  the  nerve  centers.  A  double 
series  of  sympathetic  ganglia  extends  along  the  dorsal 
wall  of  the  body  cavity,  and  sends  nerves  to  the  digestive 
and  reproductive  organs. 

The  five  senses  of  man  are  probably  possessed  in  vary- 
ing degrees  by  all  other  vertebrates,  and  each  of  the 
five  is  probably  keener  in  some  other  animal  than  in 
man. 

Of  the  higher  possibilities  of  the  vertebrate  brain  it  is 
impossible  to  speak  here.  Volumes  would  be  required  to 
adequately  summarize  the  wonderful  and  infinitely  varied 
instincts  of  fishes,  batrachians,  reptiles,  birds,  and  mam- 
mals. A  few  of  these  have  been  pointed  out  in  the  cases 
of  the  types  studied  :  others  invite  study  in  every  locality, 
on  every  hand.  Such  study  will  not  be  amiss  if  it  lead 
to  the  study  of  the  instincts  that  move  men.1  It  will  be 
especially  valuable  if  the  student  see,  that  in  proportion 
as  man  learns  to  govern  his  instinctive  impulses,  and  be- 
comes a  creature  of  ideals,  he  ascends  above  the  level  of 
the  brute. 

1  For  a  good  discussion  of  this  subject,  the  student  is  referred  to  the 
closing  chapters  of  Chadbourne's  Instinct  in  Animals  and  in  Man. 


264  VERTEBRATES. 

Evolution.  —  In  animal  structure  the  student  cannot 
fail  to  discover  increasing  complexity.  That  there  is 
not  one  single  complete  and  uniform  series  from  the  low- 
est to  the  highest,  is  true ;  but  that  there  is  more  or  less 
regular  gradation,  is  unmistakable.  In  the  embryonic 
life  of  one  of  the  higher  animals  there  is  corresponding 
gradation.  In  the  development  of  the  original  single  cell 
(the  oosperm)  there  is  increasing  complexity  of  structure, 
and  the  main  types  of  structure  found  in  other  animals 
lower  in  the  series  are  one  by  one  roughly  repeated. 
Geology  presents  a  corresponding  gradation  in  the  forms 
of  life  which  have  appeared  at  different  periods  of  the 
earth's  history,  and  plainly  shows  that  the  present  fauna 
of  the  earth  is  not  like  that  of  any  preceding  geologic 
period.  The  fossil  remains  of  animals  preserved  in  the 
rocks  show  in  a  general  way  that  the  simpler  forms  ap- 
peared first,  and  that  the  most  complex  are  of  most  recent 
introduction.  These  facts,  and  others,  seem  to  indicate 
that  there  has  been  a  continual  progressive  development 
of  animals  from  simple,  primitive  forms ;  and  such  devel^ 
opment  is  denoted  by  the  term  evolution.  A  partial  ex- 
planation  of  the  manner  in  which  evolution  may  have 
come  about  is  found  in  the  law  of  natural  selection, 
which  assumes  that  indefinite  variations  in  animals  are 
continually  occurring,  and  shows  that  such  variations  in 
structure  as  fit  an  animal  better  for  maintaining  its  place 
in  nature  will  be  preserved  through  successive  genera- 
tions, and  may  become  permanent.1 

Animals  and  Plants.  —  In  the  foregoing  pages  plant 
life  has  been  but  incidentally  referred  to,  yet  enough  has 
been  said  to  suggest  the  close  interdependence  of  plants 

1  For  a  concise  and  able  exposition  of  this  law,  the  student  is  recom- 
mended to  read  the  chapter  on  "Natural  Selection"  in  Morgan's  Animal 
Life  and  Intelligence. 


THE   LIFE  PROCESS   IN  VERTEBRATES.  265 

and  animals.  If  a  like  study  of  typical  plants  were  made, 
it  would  reveal  a  corresponding  gradation  in  form  and 
function  from  the  lowest  to  the  highest.  It  would  lead 
us  to  the  conclusion  that  the  plant  life  of  the  present  ia 
related  to  that  of  the  past  by  direct  descent.  We  should 
find  protoplasm  the  physical  basis  of  plant  life,  and  the 
cell  the  unit  of  plant  structure ;  and  at  the  bottom  of 
the  series  we  should  discover  that  there  are  free  plant 
cells  which  move  about  by  pseudopodia  and  by  cilia, 
arid  so  combine  in  themselves  the  characters  by  which  we 
commonly  distinguish  animals  from  plants,  that  we  are 
almost  unable  to  determine  what  characters  predominate. 
We  thus  come  to  the  conclusion  that  life  is  a  unit,  and 
that  the  higher  and  familiar  forms  are  at  extremes  of  the 
divergent  paths  along  which  it  has  progressed. 

The  study  of  animals  should  lead  to  a  better  under- 
standing of  man  in  his  physical  relationships.  Not  the 
remotest  object  of  the  foregoing  course  is,  that  it  shall 
serve  as  an  introduction  to  the  elementary  study  of  human 
anatomy  and  physiology.  The  lowest  animals  have  some 
points  of  structure  or  of  function  in  common  with  man ; 
and  these  points  become  more  numerous  and  more  ap- 
parent as  we  ascend  the  animal  scale,  until  the  greater 
part  of  all  that  is  written  in  the  chapter  concerning  the 
rabbit  will  apply  almost  equally  well  to  the  study  of  the 
human  body.  The  human  body  is  governed  by  the  same 
laws,  subject  to  many  of  the  same  necessities,  and  influ- 
enced by  many  of  the  same  instincts,  as  affect  other 
animal  bodies  ;  and  the  student  should  know  that  it  is  on 
the  normal  healthful  activity  of  this  animal  body  that  all 
the  possibilities  of  happiness  and  usefulness  in  human  life 
depend. 


ECHINODERMS. 

THE   STARFISH. 

(Asterias.') 

Haunts  and  Habits. — Dwellers  by  the  sea  are  familiar 
with  the  curious  red  "sea  stars,"  "starfishes,"  or  "five 
fingers,"  as  they  are  popularly  known,  which  settle  in 
troops  upon  the  beaches  at  times,  with  the  wash  of  cur- 
rents and  tides.  Along  the  northern  coast  of  New  Eng- 
land they  are  very  common.  They  should  be  studied 
alive  if  possible,  and  in  their  native  haunts ;  for,  from  the 
dried  or  alcoholic  specimens  common  in  collections,  one 
will  obtain  but  a  poor  notion  of  the  life  these  creatures 
lead.  Upon  the  beach  one  may  see  them  sprawling  flat 
upon  the  sand,  or  slowly  crawling  over  and  among  the 
rocks  with  their  arms,  which  are  so  rigid  in  preserved 
specimens,  bent  in  a  great  variety  of  positions.  One  may 
sometimes  be  found  with  its  arms  folded  about  an  oyster 
or  other  mollusk  on  which  it  is  feeding. 

Study  of  the  Live  Specimen.1 — 1.  Observe  a  fringe  of 
active  cylindrical  worm-like  process  about  the  tip  of  each 
arm  of  a  moving  starfish.  These  are  its  tube  feet.  In  an 

1  Live  starfishes  may  be  brought  into  the  laboratory  and  kept  alive  for 
several  days  if  kept  in  a  sufficient  quantity  of  sea  water,  or  if  the  supply 
of  oxygen  in  the  water  be  once  in  a  while  renewed  (as  by  dipping  and 
pouring  it  back  into  the  vessel  from  some  little  height  above  the  surface). 
They  may  be  had  alive  at  some  distance  in  the  interior  if  shipped  in  kegs 
of  sea  water,  and  studied  very  soon  after  their  arrival. 

260 


THE   STARFISH. 


267 


upturned  arm  note  that  these  spring  from  a  groove  which 
extends  along  the  lower  side  of  the  arm  its  entire  length. 
Observe  that  these  tube  feet  are  pushed  out  and  drawn  in 


STARFISH. — 1.  Starfish  (Asterias  vulgaris),  a  large  dried  specimen  one  half 
natural  size.  2.  Diagram  of  cross  section  of  oral  part  of  an  arm :  br, 
branchial  tentacle ;  sk,  calcareous  plate  of  skeleton  (in  heavy  black)  ;  sp, 
spines  (those  designated  are  on  an  adambulacral  plate);  amp,  ampullae; 
c,  radial  canal;  n,  radial  nerve;  amb,  ambulacra,  or  tube  feet.  3.  Dia- 
gram of  water-vascular  system:  ra,  madreporite;  sc,  stone  canal;  coc,  cir- 
cumoral  canal;  re,  radial  canal;  amp,  ampullae ;  amb,  ambulacra. 
4.  Starfish  infolding  an  oyster  preparatory  to  eating  it.  5.  Diagram  of 
parts  of  digestive  and  reproductive  organs,  etc.:  st,  stomach;  h,  hepatic 
caeca ;  o,  ovaries ;  amp,  ampullae ;  ambp,  ambulacral  plates  as  seen  when 
ampullae  are  removed. 

and  turned  about  freely,  and  that  in  locomotion  they  are 
advanced  in  the  direction  in  which  the  animal  is  moving, 
attached  by  means  of  terminal  disks,  and  then  contracted, 


268  ECHINODERMS. 

drawing  the  body  of  the  animal  forward  with   a  slow, 
gliding  motion. 

2.  Turn  an  active  starfish  upside  down,  and   observe 
how  the  arms  are  bent,  and  the  tube  feet  used  in  righting 
itself. 

3.  Place  a  live  specimen  in  a  shallow  dish  of  sea  water, 
and  with  a  lens  examine  it  very  near  the  surface  of  the 
water,  to  find  about  the  bases  of  the  rigid,  blunt,  conspic- 
uous spines  numerous  smaller  ones,  some  of  which  are  two- 
parted  at  the  tip  (pedicellarice),  and  which  are  continually 
snapping.     These  are  believed  to  keep  the  surface  clean 
by  preventing  a  deposition  of  sediment. 

4.  Observe   also  between   the   blunt  spines   numerous 
conic  or  cylindric  soft  membranous  processes,  protruding 
sacs  filled  with  fluid  (branchial  tentacles).     Test  the  sen- 
sitiveness of  these  and  of  the  tube  feet  to  touch. 

External  Features.  —  Use  either  alcoholic  l  or  freshly 
chloroformed  specimens,  the  latter  when  readily  obtain- 
able. Observe  :  — 

1.  That  the  flattened   body  consists  of   a  disk  and  a 
number  of  radiating  arms.    Are  the  number  and  size  of 
these  the  same  in  all  specimens  ? 

2.  That  it  presents  two  well-marked  surfaces  :  — 

(a)  A  flat  surface  on  which  it  crawls,  in  the  center  of 
which  is  the  mouth,  and  from  this  fact  called  the  oral  surface. 
(6)  A  concave  upper  aboral  surface. 
On  the  oral  surface  note  :  — 

1.  The  round  mouth,  with  the  thin  crumpled  walls  of 
the  stomach  often  seen  protruding  from  it. 

2.  The   deep   and   wide   grooves   extending   from   the 
mouth  to  the  tip  of  each  arm.     As  these  lodge  the  tube 
feet,  or  ambulacra,  they  are  called  ambulacral  grooves. 

1  If  alcoholic  specimens  have  acquired  a  disagreeable  smell,  this  may 
be  overcome  by  adding  a  few  drops  of  oil  cassia  to  the  alcohol. 


THE   STARFISH.  269 

3.  The  slender  and  somewhat  movable  spines  which 
border  the  grooves,  and  which  may  be  approximated  to 
cover  the  retracted  tube  feet. 

On  the  aboral  surface  note  :  - 

1.  A  low  convex  tubercle  located  between  the  center  of 
the  disk  and  the  junction  of  two  of  the  arms.     This  is 
the  madreporite   (named  from  its  superficial  likeness  to 
madrepore  coral).     Examine  with  a  lens. 

2.  At   the  tip   of    each   arm   a   minute   reddish   spot, 
the  eye. 

3.  Note  again  the  arrangement  of  spines  and  branchial 
tentacles. 

Internal  Anatomy.  —  Divide  the  crust  along  the  lateral 
margins  and  across  the  tip  of  the  two  arms  which  border 
the  madreporite  between  oral  and  aboral  surfaces,  being 
very  careful  to  cut  no  deeper  than  the  crust.  Continue 
the  cut  entirely  around  the  disk  and  across  the  bases  of  the 
other  arms.  Then  make  a  shallow,  circular  cut  around 
the  madreporite,  so  that,  when  the  loosened  aboral  crust  is 
lifted,  this  will  remain  in  place.  Then  carefully  lift  the 
crust,  beginning  at  the  end  of  an  arm,  looking  beneath  it 
as  it  is  lifted,  and  freeing  it  from  all  its  attachments. 
Observe  that  a  pair  of  glandular  organs  (hepatic  cceca)  in 
each  arm  lifts  with  the  crust,  being  suspended  from  it 
by  membrane  (mesentery).  Along  with  these,  and  lying 
above  them,  may  be  found  also  a  pair  of  paler  and  more 
granular  reproductive  organs.  As  the  crust  is  lifted, 
the  hepatic  caeca  may  be  traced  to  their  union  in  the  base 
of  the  arms  before  entering  the  stomach.  The  repro- 
ductive organs  may  be  traced  to  their  (ovi-  or  sperm-) 
ducts,  which  diverge  on  reaching  the  disk,  each  passing  to 
meet  at  its  external  aperture  the  duct  of  a  similar  organ 
in  the  adjacent  arm.  As  the  crust  of  the  disk  is  lifted, 
there  may  be  found  the  narrow  terminal  portion  of  the 


270  ECHINODERMS. 

alimentary  canal  attached  at  its  minute  anal  opening  on 
the  aboral  surface. 

The  Digestive  System. — With  the  aboral  crust  properly 
removed,  the  digestive  organs  will  be  fully  disclosed. 
Oral  and  aboral  openings  of  the  alimentary  canal  have 
been  noted.  By  probing  with  a  stiff  wax-tipped  bristle 
through  the  mouth,  learn  how  restricted  are  esophageal 
and  intestinal  areas  of  the  alimentary  canal,  and  how  very 
capacious  and  wide  is  the  stomach.  In  the  latter  find  :  — 

1.  A  loose,  baggy  oral  portion  which  may  be  protruded 
through   the   mouth,  and  which   has  muscles  for  its  re- 
traction.      In  feeding,  the  starfish  commonly  protrudes 
this  portion  out  of  its  mouth  and  in  between  the  valves 
of  the  shell,  and  digests  the  oyster  there. 

2.  An  aboral  portion  of  more  definite  shape,  with  which 
the  hepatic  caeca  communicate.     Probe  the  ca3ca. 

The  Water- Vascular  System.  —  Study  this  in  an  injected 
specimen.1  Observe  :  — 

1.  A  vessel  extending  downward  from  the  madreporite 
beside  the  stomach  toward  the  mouth.     This  is  the  stone 
canal,  so  called  because  calcareous  matter  is  found  in  its 
walls. 

2.  Circumoral  canal,  into  which  the  stone  canal  opens. 

3.  A  series    of   radial  canals  extending  outward  from 
the  circumoral  canal,  lodged  deep  in  the  ambulacra]  groove 
on  the  underside  of  each  arm. 

4.  A  double  row  of   round  water  sacs  called  ampullae 
within  each  arm  on  its  floor  on  either  side  of  a  median  ridge. 

5.  Two  double  rows  of  ambulacra,  or  tube  feet,  in  cor- 
responding position  on  the  oral  surface  of  each  ray.     Snip 

1  The  water-vascular  system  may  be  injected  by  inserting  a  cannula 
into  each  radial  canal  near  the  tip  of  the  arm,  and  injecting  toward  the 
disk,  forcing  the  water  out  at  the  madreporite. 


THE   STAKFISH.  271 

off  the  tip  of  a  tube  foot,  and,  by  probing  through  it  with 
a  slender  bristle,  determine  its  relation  to  the  ampullae 
above.  Determine  the  relation  of  the  ampullae  to  the 
radial  canal.  Pull  off  a  tube  foot  entire,  and  dissect  it  in 
a  drop  of  clove  oil  or  glycerine,  under  a  lens,  to  see  the 
delicate  muscle  fibers  in  its  walls,  and  the  oblique  fibers 
near  its  tip,  which  are  inserted  into  the  middle  of  the  ter- 
minal disk.  How  does  the  starfish  maintain  its  foothold  ? 

Circulatory  System.  —  Beside  the  stone  canal,  there  may 
be  seen  in  a  starfish  that  has  been  opened  alive  a  delicate 
pulsating  tube,  sometimes  called  the  heart.  The  blood 
vessels  which  run  out  from  this  are  so  minute  as  to  be 
traceable  only  by  sectioning. 

Nervous  System.  —  A  portion  of  the  nervous  system 
may  be  seen  on  the  oral  surface  without  dissection,  as  it 
is  covered  only  by  transparent  epithelium.  Find  :  — 

1.  A  circumoral  nerve  wing. 

2.  Radial  nerves  extending  out  from  the  latter  along 
the  oral  side  of  the  radial  canals  to  the  tip  of  the  arms. 

3.  Masses  of  nerve  tissue,  called  ganglia,  at  the  junction 
of  the  radial  nerves  with  the  circumoral  ring. 

4.  A  pigmented  spot,  called  the  eye,  at  the  distal  end 
of  each  radial  nerve. 

The  Body  Wall.  —  If  almost  any  portion  of  the  body 
wall  be  examined  in  cross  section,  about  three  layers  will 
be  distinguished  in  it. 

1.  A   tough   outer   membranous   layer    of    epithelium 
covering  the  whole  animal  except  the  spines. 

2.  A  middle  layer  of   connective  tissue,  in  which  are 
imbedded  the  calcareous  plates  which  make  up  the  hard 
parts  of  the  skeleton. 

3.  A  thin  lining  layer  of  peritoneal  epithelium.     This 


272  ECHINODERMS. 

is  pushed  out  through  holes  in  the  middle  layer  to  line 
the  branchial  tentacles,  and  is  infolded  to  form  the  mesen- 
teries. Pass  a  slender  probe  into  a  branchial  tentacle. 

Boil  a  portion  of  an  arm  in  potash  solution,  to  remove 
the  connective  tissue  which  holds  together  the  calcareous 
plates.  When  these  seem  about  ready  to  fall  apart,  wash 
and  separate  them,  to  see  how  they  are  put  together. 
Find  :  — 

1.  A  double  row  of  ambulacral  plates,  meeting  by  their 
ends  at  an  obtuse    angle  to  form  the  gable  roof   of  the 
ambulacral  furrow. 

2.  On   either   side   a   bordering   row   of   adambulacral 
plates. 

3.  Other  plates  irregularly  disposed  in  other  portions  of 
the  body  wall. 

What  is  the  shape  of  the  plates  of  all  these  sorts,  and 
how  are  they  put  together? 

Between  the  walls  of  the  alimentary  canal  and  the  body 
walls  is  a  distinct  body  cavity  which  the  blood  (hemo- 
lympTi)  occupies.  The  hepatic  cseca  and  the  reproductive 
organs  are  extended  laterally  into  it,  as  already  noted. 

Life  Process.  —  Only  in  the  details  for  carrying  out 
the  vital  processes  do  we  find  anything  new  or  unusual  in 
the  starfish. 

I.  Nutrition.  —  The  digesting  of  a  mollusk  in  its  own 
shell  without  having  been  swallowed  is  unusual ;  but,  when 
we  remember  that  digesting  is  mainly  dissolving  prepara- 
tory to  absorbing,  we  see  that  the  difference  is  merely  one 
of  position.  Digested  food  passes  directly  into  the  blood 
by  osmosis,  and  is  carried  with  currents  set  up  by  the  feebly 
pulsating  circulatory  apparatus.  In  the  branchial  tentacles 
it  is  properly  exposed  for  aeration ;  and  in  all  the  tissues, 
as  ever,  its  constituents  are  selected  by  the  individual 
cells  for  use. 


THE    STARFISH.  273 

II.  Reproduction.  —  Ova  and  sperms  in  immense  num- 
bers escape  into  the  water,  where  fertilization  takes  place. 
The  resulting  oosperm  in  its  development  passes  through 
the  segmentation  and  gastrulation  stages  described  for 
the  snail  (pp.  158,  159),  the  irregularities  there  noted 
being  absent  from  the  more  typical  development  of  the 
starfish.  The  gastrula  develops  into  curious  larval  forms 
{Bipinnaria  and  Brachiolaria),for  description  of  which  the 
student  is  referred  to  the  larger  text-books  of  zoology. 
The  larval  forms  are  strictly  bilateral.  Were  it  not  for 
the  persistent  bilaterality  of  the  water-vascular  system, 
the  symmetry  of  the  adult  would  be  radial.  The  change 
from  larval  to  adult  form  is  so  great  as  to  simulate  meta- 
morphosis. 

Lost  parts,  especially  arms,  are  readily  reproduced. 

Voluntary  Motion  and  Sensation  present  no  important 
phases  not  already  noted  in  preceding  pages. 

The  starfish  is  a  representative  of  the  large  group 
Echinodermata,  a  group  which  has  no  fresh-water  rep- 
resentative. Other  echinoderms  are  crinoids,  sea  urchins, 
and  sea  cucumbers. 

NEED.  ZOOL. 18 


APPENDIX. 


PREREQUISITES. 

In  order  to  use  this  book  advantageously,  there  will  be  needed  :  — 

1.  In   Charge   of  the   Course. —  A   teacher  with    some   time   and 
opportunities  at  his  disposal  for  acquainting  himself  and  his  classes 
with  the  fauna  of  his  locality. 

2.  In  the  Laboratory.  —  Plenty  of  light;   plain  desks  or  tables  at 
which  students  may  work ;   a  few  good  microscopes,  with  the  usual 
accessories,  —  slips,  covers,  watch  glasses,  pipettes,1  etc.;    the  simple 
reagents  described  on  pp.  276  and  277  ;  a  water  supply;  receptacles  for 
organic  refuse.1 

3.  In  the  Hands  of  every  Student.  —  A  good  lens ;  a  scalpel;  a  small 
pair  of  sharp-pointed  dissecting  scissors  ;  several  dissecting  needles ; l 
a  small  forceps ; l  bristles  for  probing ; a  notebooks  and  pencils,  for 
descriptions  and  drawings. 

4.  In  the  Library.  —  A  few  good  books  of  reference.     All  of  the 
following  are  recommended  :  — 

Lang's  Text-book  of  Comparative  Anatomy.     Recent  and  standard, 

but  expensive.     (Macmillan  &  Co.,  New  York.) 
Marshall  and  Hurst's  Practical  Zoology.     $3.50.      (G.  P.  Putnam's 

Sons,  New  York ;   Smith,  Elder,  &  Co.,  London.) 
McMurrich's  Invertebrate  Morphology.     $4.     (H.  Holt  &  Co.,.  New 

York.) 
Thomson's  Study  of  Animal  Life.     $1.50.     (Charles  Scribner's  Sons, 

New  York.) 
Jordan's  Manual  of  the  Vertebrates.     $2.50.     (A.  C.  McClurg  &  Co., 

Chicago.) 

Edward  Potts's  Monograph  of  the  Fresh  Water  Sponges.  $1.    (Obtain- 
able from  the  author,  at  228  South  Third  Street,  Philadelphia.) 
jCornstock's  Manual  for  the  Study  of  Insects.     $3.75  net.     This  book 

is  especially  commended  to  the  general  student  of  entomology. 

(Comstock  Publishing  Co.,  Ithaca,  N.Y.) 

1  See  note  on  cheap  apparatus,  p.  287. 
275 


276  APPENDIX. 

French's   Butterflies   of    the   Eastern    United    States.     $2.      (J.   B. 

Lippincott  Co.,  Philadelphia.) 

Stoke's  Microscopical  Praxis.     $1.50.     (E.  Bigelow,  Portland,  Conn.) 
Darwin's  Vegetable  Mould  and  Earthworms.     $1.50.     (D.  Appletoii 

&  Co.,  New  York.) 
Tryoii's  Structural  and  Systematic  Conchology.     (Obtainable  through 

the  Academy  of  Sciences,  Philadelphia.) 
Coues's  Key  to  North  American  Birds.    $7.50.     (Estes  &  Lauriat, 

Boston.) 
Mivart's  American  Types  of  Animal  Life.    $2.     (Little,  Brown,  & 

Co.,  Boston.) 
Wilder  and  Gage's  Anatomical  Technology.     $4.50.     (A.  S.  Barnes 

&  Co.,  New  York.) 

Chadbourne's  Instinct.    $2.50.     (G.  P.  Putnam's  Sons,  New  York.) 
Morgan's   Animal  Life  and  Intelligence.     $4.     (Ginn  &  Co.,  Bos- 
ton.) 
Davie's  Nests  and  Eggs  of  North  American  Birds.     (Oliver  Davie  & 

Co.,  Columbus,  O.) 
Davie's  Methods  in  the  Art  of  Taxidermy.     The  best  book  of  its 

kind  that  has  yet  appeared.     (Oliver  Davie  &  Co.,  Columbus,  O.) 
Bates's  Naturalist  on   the   Amazons.    $1.50.     A  zoological  classic. 

(Roberts  Bros.,  Boston.) 


REAGENTS. 

The  following  reagents  and  mounting  media  should  be  kept  in 
well-stoppered  bottles,  always  available  for  use.  They  should  be  used 
sparingly;  but  a  quantity  of  any  reagent,  once  used,  should  never  be 
poured  back  into  the  stock  bottle. 

Normal  Salt  Solution.  —  This  is  a  f-per-cent  solution  of  common 
salt  in  water.  It  is  useful  as  a  mounting  medium  in  which  to  exam- 
ine, microscopically,  fresh  tissues,  which  wTould,  like  blood  corpuscles, 
be  destroyed  by  the  osmotic  action  of  pure  water. 

Magenta.  —  A  strong  aqueous  solution.  This  is  useful  for  staining 
fresh  tissues  for  microscopic  examination. 

Methyl  Green.  —  A  strong  aqueous  solution,  improved  by  the  addi- 
tion of  1  per  cent  acetic  acid.  This  is  a  good  and  permanent  stain 
for  either  fresh  or  preserved  tissues.  It  stains  nuclei  deeply,  and  is 
therefore  very  useful  for  examining  amoeba,  pararnecium,  etc. 

Hydrochloric  Acid.  —  Diluted  with  water,  this  is  very  useful  for 


REAGENTS.  277 

decalcifying  the  armor  of  crustaceans,  the  shells  of  mollusks,  and  the 
bones  of  vertebrates. 

Nitric  Acid.  —  This  acid  may  be  used  for  decalcifying,  but  it  is 
more  expensive  than  hydrochloric.  A  10-per-cent  solution  is  useful 
for  macerating  other  tissues  preparatory  to  a  dissection  of  the  ner- 
vous system.  If  the  bodies  of  small  animals  are  kept  in  it  for  two 
or  three  days,  its  destructive  action  on  other  tissues  will  leave  the 
nerves  more  easily  accessible.  Strong  nitric  acid  is  used  for  isolating 
the  spicules  of  fresh-water  sponges. 

Glycerine.  —  This  is  a  very  useful  fluid  in  which  to  examine  small 
objects  microscopically.  A  25-per-cent  solution  greatly  increases  the 
transparency  of  small  objects  soaked  in  it,  making  the  structure  more 
evident. 

Canada  Balsam.  —  A  sirupy  solution,  made  by  dissolving  the  dried 
resin  in  turpentine  or  xylol,  is  an  invaluable  medium  for  making 
permanent  mounts  of  microscopic  objects.  Both  air  and  water  must 
first  be  removed  from  the  objects  to  be  mounted  in  it.  Hard,  diy 
objects,  such  as  the  claws  of  insects  and  the  isolated  spicules  of 
sponges,  may  be  placed  in  a  drop  of  balsam  on  a  slip,  heated  gently 
over  an  alcohol  lamp  or  Bunsen  burner  to  expel  all  air,  and  covered 
with  a  thin  cover  slip ;  but  a  less  direct  method  must  be  employed 
in  mounting  soft  tissues.  These  must  be  covered  first  with  weak, 
and  afterward  with  strong,  alcohol,  to  remove  the  water  they  contain. 
They  must  then  be  removed  from  alcohol  into  turpentine  or  xylol 
for  clearing.  They  may  then  be  placed  in  a  drop  of  balsam  on  a 
slide,  and  at  once  covered. 

Chloroform  is  very  useful  for  removing  excess  of  balsam  from  slips. 

Alcohol.  —  The  use  of  alcohol  in  dehydrating  tissues  for  mounting 
in  balsam  has  already  been  stated.  But  one  other  of  its  many  uses 
in  the  laboratory  will  be  mentioned  here,  —  its  use  in  preserving 
specimens.  In  this  use  its  action  is  the  same  as  in  the  preparation 
of  specimens  for  mounting.  It  preserves  objects  by  removing  the 
water  from  them.  It  removes  the  water  by  osmosis,  and  it  is  there- 
fore weakened  every  time  it  is  used  by  just  so  much  water  as  it  takes 
from  the  tissues.  Two  grades  of  alcohol  should  ordinarily  be  used 
for  preserving  specimens,  —  a  weaker  grade,  in  which  the  dehydration 
is  begun,  and  a  stronger  grade,  into  which  they  may  be  transferred 
from  the  weaker,  for  permanent  preservation.  Alcohol  of  70  to  80  per 
cent  strength,  after  osmotic  action  has  ceased,  is  strong  enough  for 
permanent  preservation. 

Turpentine,  Xylol,  Chloroform,  Ether,  etc.,  are  used  in  their  com- 
mercial form,  as  directed  in  the  text. 


278  APPENDIX. 


DIRECTIONS  FOR   THE  PREPARATION   OF  MATERIAL  FOR 

STUDY. 

The  following  directions  are  placed  in  the  Appendix,  because  it 
has  not  been  found  practical  to  have  them  carried  out  by  beginners 
in  zoology.  They  are  therefore  intended  for  the  teacher  or  for  his 
assistants.  Anticipating  that  this  book  will  fall  into  the  hands  of 
some  teachers  who  are  not  at  all  familiar  with  zoological  laboratory 
methods,  a  few  of  the  simplest  are  given  in  the  following  notes,  with 
much  detail  which  would  be  unnecessary  were  all  who  are  called 
upon  to  teach  zoology  fitted  for  the  task  by  a  laboratory  training. 
If  the  methods  given  below  are  not  in  all  cases  the  best  methods 
known  to  science,  they  are  believed  to  be  the  best  that  can  be  well 
applied  with  such  equipment  as  is  usually  provided  for  elementary 
work  in  zoology. 

I.  On  finding  Amoeba.  —  The  amoeba  lives  in  the  superficial  ooze  of 
ponds  and  ditches  everywhere,  but  it  is  not  often  very  abundant.  It 
may  be  most  easily  obtained  from  shallow  pools.  To  get  it,  scrape  up 
the  superficial  ooze  from  the  bottom  of  the  pool,  avoiding  the  mud  that 
underlies  the  ooze,  and  place  in  a  shallow  dish  with  water.  Allow  the 
ooze  to  stand  undisturbed  for  a  day  or  two.  The  amoebas  will  then 
have  come  to  the  top  of  the  ooze,  whence  they  may  be  taken  up  with 
a  dropping  tube.  Place  small  drops  —  water,  ooze,  sediment  and  all 
—  on  separate  glass  slips,  and  cover  each  with  a  thin  glass  cover  slip. 
The  sediment  in  the  drops  will  prevent  the  cover  slips  from  crushing 
the  amoebas.  The  slips  may  then  be  searched  quite  rapidly,  and 
amcebas  recognized,  with  a  power  of  250  diameters.  A  practiced  eye 
will  recognize  them  with  much  lower  power ;  but  the  eye  that  does 
not  know  just  what  to  look  for  may  pass  them  over  even  with  this 
amount  of  magnification.  Higher  powers  cannot  be  used  in  searching 
the  field  over  without  too  great  expenditure  of  time.  The  beginner's 
trouble  comes  from  the  unlikeness  of  the  clear  jelly-like  mass  spread- 
ing over  the  glass  slip  to  anything  commonly  denoted  by  the  term 
"animal." 

Amcebas  are  found  also  in  the  slime  that  covers  the  stems  and 
leaves  of  some  submerged  plants,  and  in  the  thin  scum  on  the  surface 
of  the  water.  The  slime  or  the  scum  may  be  collected,  and  treated 
in  the  same  way  as  the  ooze  mentioned  in  the  foregoing  paragraph. 

It  is  well  to  make  separate  collections  from  several  places,  to  insure 
finding  amoebas. 


THE   PREPARATION  OF  MATERIAL.  279 

II.  Paramecium  Culture.  —  Put   a  small  bunch    of    hay  into    a 
tumbler  of  pond  water,  and  allow  it  to  stand  in  a  warm,  well-lighted 
place  (not  in  the  direct  sunlight)  for  a  few  days  or  a  week.     This 
will  usually  be  an  unfailing  source  of  slipper  animalcules.     Drops  of 
water  taken  from  the  surface  will  be  seen  teeming  with  active  minute 
white  specks  visible  to  the  unaided  eye.     The  water  of  a  vase   in 
which  flowers  have  been  kept  too  long  will  often  furnish  an  abundant 
supply. 

These  creatures  swim  so  freely,  that  it  is  often  difficult  to  keep  one 
in  the  field  of  the  microscope.  If  a  small  tuft  of  fine  cotton  fibers 
be  lowered  into  the  drop  upon  the  slip  before  it  is  covered,  some  of 
the  animals  are  likely  to  be  entangled  in  the  meshes  of  the  cotton, 
where  they  may  be  studied  alive.  The  cotton  also  supports  the  cover 
glass,  so  that  the  animals  are  not  crushed. 

If  their  feeding  is  to  be  watched,  finely  powdered  carmine  or  indigo 
should  also  be  put  into  the  drop  before  it  is  covered. 

A  method  of  retaining  paramecium  within  the  field  for  examina- 
tion, which  usually  proves  more  satisfactory,  is  to  mount  the  animal- 
cule in  a  drop  of  gum  solution  made  by  boiling  cherry,  peach,  or 
plum  gum  in  water,  and  diluting  to  the  desired  fluidity,  and  covering. 
The  gum  retains  the  animal,  restricts  somewhat  the  action  of  the  cilia, 
and  its  refractive  properties  render  some  structures  more  evident. 

III.  On  finding  Fresh-water   Sponges.1  —  The  collector  will  need, 
first  of  all,  to  know  that  an  animal  may  be  fixed  in  position,  and  green 
in  color. 

The  sponge  recommended  for  study  in  this  course  (Myenia  fiuvia- 
tilis)  may  be  looked  for  in  the  clear  water  of  ponds  and  lakes  and 
quietly  flowing  bayous.  It  will  hardly  be  found  in  muddy  water  or 
in  shallow  water  over  a  mud  bottom.  It  grows  in  compact  or  lobed 
cushion-like  masses  (often  several  inches  in  diameter)  upon  the  stones 
of  the  bottom,  upon  "  water-logged  "  timbers,  upon  boughs  drooping 
in  the  water,  etc.  It  is  of  a  yellowish  or  brownish  or  green  color.  It 
may  be  distinguished  (under  a  lens)  from  vegetable  growths  of 
similar  appearance  by  the  absence  in  it  of  leaves  and  of  long,  thread- 
like fibers,  and  by  the  presence  of  osteoles,  of  bristling  spicule  points, 
and  (in  autumn)  of  gemmules.  Although  it  is  cosmopolitan  in  its 
range,  there  do  not  appear  to  be  many  localities  of  great  abundance  of 
it.  It  should  therefore  be  definitely  located  in  advance  of  need,  so  that 
fresh  specimens  may  be  at  once  obtainable  when  needed  for  class  use. 

1  The  author  has  drawn  largely  upon  the  excellent  monograph  by  Edward 
Potts  for  the  directions  found  in  this  and  the  next  following  sections. 


280  APPENDIX. 

In  collecting,  it  is  not  enough  to  tear  away  the  top  of  the  sponge  : 
gemmules  are  most  abundant  in  its  deepest  parts.  A  sharp  hatchet, 
with  which  a  chip  bearing  the  entire  sponge  may  be  detached  from 
submerged  timbers,  will  therefore  be  found  very  serviceable.  A  broad, 
dull  knife  blade  may  be  used  for  detaching  such  as  grow  on  large 
stones.  Specimens  will  be  gathered  most  quickly  by  wading  with 
high  boots  in  shallow  water,  and  cutting  them  free  from  chunks  and 
stones  which  lie  on  the  bottom.  They  will  be  collected  most  easily 
when  found  growing  upon  partly  submerged  boughs  of  trees,  which 
may  be  drawn  out  of  the  water. 

Specimens  may  be  preserved  in  alcohol.  The  skeletal  framework 
will  be  readily  preserved  by  drying  the  specimens  in  situations 
sheltered  from  the  direct  rays  of  the  sun. 

IV.  On  preparing  Gemmules  and  Spicules  for  Examination.  —  Dissect 
out  with  needles  half  a  dozen  gemmules  from  the  sarcode  or  from 
the  dried  sponge  mass.  Place  them  together  on  the  center  of  a  clean 
glass  slip,  and  cover  them  with  a  drop  of  boiling  nitric  acid.  After 
five  minutes  (more  or  less,  as  may  prove  necessary  time  for  rendering 
their  outer  coat  transparent  without  destroying  it)  wash  off  the  acid 
by  running  successive  drops  of  water  across  the  slide  while  holding  it 
in  an  inclined  position.  Then  cut  two  or  three  of  the  gemmules  in 
halves  or  in  quarters,  so  as  to  expose  the  edges  of  their  outer  coat. 
Then  remove  the  water,  as  much  as  possible  with  blotting  paper, 
and  the  remainder  by  adding  strong  alcohol.  Renew  the  alcohol 
once  or  twice ;  then  remove  it  with  blotting  paper,  and  cover  the 
gemmules  with  a  drop  of  turpentine  or  benzole.  After  allowing 
a  few  moments  for  the  gemmules  to  become  penetrated  with  the  oil, 
remove  excess  of  it  with  blotting  paper,  and  add  a  drop  of  balsam  and 
a  cover  glass,  and  the  preparation  will  be  properly  and  permanently 
made. 

Place  bits  of  the  sponge  containing  skeletal  spicules,  and  several 
gemmules,  together  in  a  small  test  tube,  and  boil  them  for  several 
minutes  in  a  few  drops  of  nitric  acid :  the  spicules  will  alone  remain 
undissolved.  Fill  up  the  test  tube  with  water,  heat  gently,  and  set 
aside.  The  spicules  will  settle  to  the  bottom.  After  they  have  set- 
tled, hold  the  test  tube  slightly  inclined,  and  roll  it  slowly  between  the 
fingers  to  collect  the  spicules  to  one  spot  on  the  bottom.  Holding  one 
end  of  a  small  glass  tube  closed  with  the  finger,  push  the  open  end 
down  inside  the  test  tube  to  this  spot,  and  then  lift  the  finger  at  the 
top  sufficiently  to  admit  a  drop  of  water  at  the  bottom.  This  drop 
will  carry  into  the  tube  a  load  of  spicules,  which  may  be  transferred 
to  the  center  of  a  clean  slip.  After  the  water  has  evaporated,  and  left 


THE  PREPARATION  OF   MATERIAL.  281 

the  spicules  deposited  upon  the  slip,  heat  the  slip  gently  to  make 
sure  of  the  drying,  cover  the  spicules  with  a  drop  of  balsam,  add  the 
cover  glass,  and  the  preparation  is  complete. 

V.  On  "Germinating"  the  Gemmules.  —  "To  obtain  the  young 
spongillae,  it  is  only  necessary  to  get  a  portion  of  an  old  living  speci- 
men bearing  statoblasts  (gemmules),  and,  having  taken  out  a  few  of 
the  latter,  to  roll  them  gently  between  the  folds  of  a  towel,  to  free 
them  from  all  extra  material  as  much  as  possible.  Place  them  in  a 
watch  glass,  so  as  not  to  touch  each  other,  with  a  little  water,  in  a 
saucer  or  small  dish  filled  with  small  shot  to  keep  the  saucer  upright, 
and,  covering  them  with  a  glass  shade,  transfer  the  whole  to  a  window 
bench  opposite  to  the  light.  In  a  few  days  the  young  spongilla  may 
be  observed  (from  its  white  color)  issuing  from  the  statoblast  (gern- 
mule),  and  gluing  the  latter  as  well  as  itself  to  the  watch  glass,  when 
it  is  ready  for  transfer  to  the  field  of  the  microscope  for  examination, 
care  being  taken  that  it  is  never  uncovered  by  water,  which  may  be 
replenished  as  often  as  necessary."  —  H.  J.  CARTER,  ESQ.,  of  Devon- 
shire, England,  in  Annals  and  Magazine  of  Natural  History  for  1882, 
p.  365. 

"  If  a  few  of  them  (gemmules)  are  removed  from  a  fresh  sponge, 
placed  in  an  open  stage  tank  (or  watch  glass)  covered  with  water 
(preferably  rain  water),  and  protected  from  dust  and  too  rapid  evapo- 
ration by  a  cover  of  common  glass,  and  placed  upon  a  window  ledge 
but  not  in  direct  sunlight,  the  following  phenomena  may  be  confi- 
dently expected. 

"  We  are  supposed  to  be  working  with  gemmules  heavier  than  water, 
beneath  which  they  are  allowed  to  rest  quietly.  If  in  a  few  days  or 
hours  some  of  the  gemmules  are  found  fixed  where  they  lie,  it  is 
probable  that  germination  has  begun.  On  removing  the  preparation 
to  the  stage  of  the  microscope,  the  instrument  being  fixed  in  vertical 
position,  the  initial  stages  of  the  development  of  a  sponge  can  be 
daily  or  hourly  watched  under  low  powers  of  magnification. 

"  A  creamy  white  granular  film  first  appears,  and  gradually  surrounds 
the  gemmule,  then  widens,  spreading  irregularly  in  various  direc- 
tions, reminding  one  of  the  appearance  of  a  giant  amoeba.  At  first 
nearly  uniform  in  texture  and  density,  it  will  soon  be  seen  that  the 
interior  portion  is  more  compact  than  the  superficies,  a  very  delicate 
film  being  set  off  around  and  over  it,  puffed  up  at  one  subcentral 
point  into  a  greatly  elongated  rounded  cone,  open  at  the  extremity. 
Here  at  this  early  stage  is  a  complete  sponge.  The  water  with  its 
contained  nutriment  is  already  being  drawn  in  through  almost  in- 
visible pores,  and,  after  feeding  the  young  cells,  is  thrown  out  at  the 


282  APPENDIX. 

summit  of  the  cone,  technically  the  'chimney,'  just  described.  This 
motion  in  the  transparent  fluid  would  be  quite  unperceived  but  for  an 
occasional  larger  particle,  which  may  be  seen  to  come  wandering 
along  beneath  the  covering  film  until,  reaching  the  '  chimney,'  it  is 
suddenly  puffed  out  as  from  a  volcano.  If  the  young  sponge  is  very 
carefully  fed  with  finely  powdered  carmine,  or  other  suitable  (in- 
soluble) coloring  matter,  the  course  of  circulation  may  more  readily 
be  followed."  —  EDWARD  POTTS,  in  The  Microscope,  vol.  x.  p.  163. 

VI.  On  Hydra  Culture.  —  The  hydra  lives  in  shallow  ponds  and  per- 
manent pools  in  still  water.  In  warm  weather  it  is  often  found  near 
the  surface,  attached  to  the  stems  of  reeds,  or  pendent  from  the  lo\ver 
surface  of  floating  leaves.  In  winter  it  will  more  often  be  found 
attached  to  leaves,  that  have  fallen  on  the  bottom.  Its  narrow,  cylin- 
drical body  is  about  half  an  inch  long,  its  tentacles  are  of  equal  length, 
and  its  color  is  pale  brown,  or,  in  another  species,  clear  green.  The 
leaves,  etc.,  should  be  drawn  out  of  the  water,  and  their  surfaces 
examined  with  a  lens.  The  hydras,  if  present,  will  be  much  con- 
tracted after  being  disturbed ;  but  the  tentacles  do  not  entirely  dis- 
appear when  contracted,  but  remain  as  a  circle  of  fleshy  knobs  about 
the  free  end  of  the  hydra,  and  these  will  serve  for  recognition.  If 
the  leaves  be  placed  in  a  jar  of  water,  the  hydras  will  extend  them- 
selves again  in  a  few  minutes. 

Perhaps  the  surest  way  to  find  them  is  to  place  the  leaves,  etc.,  in  a 
shallow  white  dish  or  plate  in  water  for  a  few  minutes.  If  present, 
they  will  extend  themselves  when  quiet,  and  may  easily  be  seen  upon 
a  white  background.  Though  not  abundant  anywhere,  there  is  hardly 
a  locality  that  will  not  furnish  a  good  supply  after  a  proper  search. 
They  are  very  apt  to  be  found  year  after  year  in  the  same  places. 

Hydras  for  class  use  should  be  collected  a  week  or  more  before  they 
are  to  be  used.  They  may  be  kept  in  a  jar  of  water,  or  aquarium,  in 
which  some  small  aquatic  plants  are  placed.  They  will  need  to  be 
supplied  with  food.  They  eat  readily  small  crustaceans  not  larger 
than  cyclops,  daphnia,  etc. ;  also  protozoans  and  microscopic  plants. 
If  the  jar  in  which  they  are  to  be  kept  be  taken  to  the  field  and  filled 
with  the  water  in  which  they  are  found,  and  a  few  of  the  plants  to 
which  they  adhere,  sufficient  food  to  keep  them  for  a  long  time  will  prob- 
ably be  taken  up  with  the  water  and  the  plants.  None  of  the  larger 
animals  (e.g.,  snails)  which  feed  on  hydras  should  be  left  in  the  jar. 

Many  of  the  hydras  will  attach  themselves  to  the  sides  of  the  jar, 
on  the  side  toward  the  light.  When  wanted  for  study,  they  may  be 
dislodged  by  pushing  a  knife  blade  between  their  bases  and  the  glass, 
and  taken  up  with  a  dropping  tube. 


THE  PREPARATION  OF    MATERIAL.  283 

VII.  On  Mounting  Insects.1  —  A  few  simple  directions  will  be  suffi- 
cient  guide  to  the  preparation  of  the  few  life-history  boxes   men- 
tioned in  this  book.     The  steps  in  the  process  are  (1)  the  fixing  of 
the  specimens  on  pins ;    (2)  the  thorough  drying  of  them ;    and  (3) 
the   mounting  of  them,  under  glass,  in  a  box  of  some  sort,  tightly 
sealed  to  keep  out  pests. 

Most  specimens  may  be  fixed  on  pins  run  vertically  through  the  thorax 
two  thirds  of  their  length.  Beetles  (with  wings  closed)  should  have 
the  pins  run  through  the  center  of  the  left  wing  cover,  and  obliquely 
downward  through  the  body.  Minute  specimens  may  be  fixed  with 
mucilage  on  a  narrow  strip  of  white  paper,  through  which  the  pin 
may  be  stuck.  Pins  of  uniform  length  (preferably  insect  pins)  should 
be  used,  and  the  mounted  specimens  should  stand  at  the  same  height 
on  all  the  pins.  When  the  wings  of  an  insect  are  to  be  spread  and 
dried  so,  a  setting  board  is  necessary.  The  pin  is  run  through  the 
insect  in  the  usual  way.  The  body  is  placed  in  a  groove  in  the  set- 
ting board,  and  the  wings  are  spread  horizontally  upon  the  board,  and 
held  in  position  by  strips  of  paper  pinned  across  their  tips. 

The  best  boxes  for  preserving  insect  specimens  are  lined  on  the 
bottom  with  sheet  cork,  into  which  the  pins  can  easily  be  pushed. 
Thin  disks,  'of  uniform  size,  cut  from  common  bottle  corks,  and 
glued  to  the  bottom  of  the  box,  will  generally  answer  the  student's 
purpose.  A  bit  of  gum  camphor  should  be  placed  in  the  box,  and 
the  top  and  all  cracks  tightly  sealed,  if  the  preparation  is  to  be  per- 
manent. 

VIII.  On  Dissecting  under  Water.  —  Small  animals  not  covered  with 
hair  or  feathers  are  best  dissected  under  water.     Delicate  parts  are 
floated  into  view,  and  more  easily  separated  and  more  easily  recog- 
nized under  water. 

Excellent  dissecting  pans  are  made  by  pouring  melted  wax  or 
paraffin e  into  a  shallow  vessel  to  harden  on  the  bottom  and  form  a 
thin  layer,  to  which  the  specimens  may  be  pinned  down.  A  piece  of 
thin  board  wedged  fast  in  the  bottom  of  a  pan  with  vertical  sides 
will  answer  every  purpose. 

The  structure  of  small  parts  may  often  be  better  made  out  by  "  teas- 
ing"; i.e.,  by  tearing  apart  with  needles  on  a  slip  in  a  drop  of  water, 
or,  better,  of  dilute  glycerine. 

1  Part  F  of  Bulletin  No.  39,  United  States  National  Museum,  entitled 
Directions  for  Collecting  and  Preserving  Insects,  contains  full  and  explicit 
directions,  as  well  as  a  fund  of  suggestions,  as  to  methods  of  rearing  insects, 
references  to  entomological  literature,  etc.  It  may  be  had  for  the  asking,  and 
a  copy  should  be  in  every  school  library. 


284  APPENDIX. 

IX.  On  Injections.  —  Blood  vessels  and  other  tubular  organs  and 
ducts  are  much  more  easily  studied  if  first  filled  with  some  colored 
substance  which  renders  them  more  conspicuous.  The  following 
Starch  Injection  Mass  is  recommended  for  filling  such  vessels :  — 

Tarta. 

Dry  (laundry)  starch 40 

Water  or  (better,  if  to  be  kept)  2i%  solution  chloral  hydrate     .        40 

95%  alcohol 10 

Color  mixture 10 

These  should  be  thoroughly  mixed  and  the  mixture  strained 
through  cheese-cloth. 

It  is  easily  prepared,  easily  used,  and,  on  the  whole,  gives  very  satis- 
factory results.  A  syringe  of  some  sort  may  be  necessary  for  forcing  the 
mass  into  the  vessels  to  be  injected.  A  cannula  should  be  attached  by  a 
short  bit  of  rubber  tubing  to  the  end  of  the  syringe.  The  cannula  is 
for  insertion  into  the  end  of  the  vessel  to  be  injected.  It  may  readily 
be  made  of  a  piece  of  glass  tubing  drawn  to  a  point,  with  a  constriction 
made  near  the  point  to  hold  a  ligature  from  slipping  off  when  tied 
around  it.  It  is  well  to  have  several  cannulae  with  nozzles  of  different 
sizes.  A  rubber  bulb  on  a  cannula  made  from  a  glass  tube  will  answer 
ordinarily  for  any  animal  not  larger  than  a  cat. 

The  formula  for  the  color  mixture  mentioned  in  the  above  is  as 
follows :  — 

Dry  color  (vermilion,  red  lead,  Berlin  blue,  ultramarine  blue,  Parts. 

chrome  yellow,  orange,  or  green) 3 

Glycerine 3 

95%  alcohol 3 

These  should  first  be  thoroughly  mixed  by  grinding  together  in  a 
mortar. 

This  starch  mass  will  keep  indefinitely  in  a  well-stoppered  bottle, 
and  only  needs  to  be  shaken  to  be  ready  for  use.  In  using  it,  the 
syringe  is  first  filled  with  it.  The  cannula  is  attached  to  the  syringe, 
filled  by  pushing  on  the  piston  slightly,  inserted  into  the  end  of  the 
vessel  to  be  injected,  and  ligatured  fast  by  a  soft  cotton  string  tied 
around  the  outside  of  the  vessel.  The  vessel  is  then  filled  by  a  steady, 
gentle  pressure  upon  the  piston  of  the  syringe. 

A  verv  convenient  instrument  for  passing  the  ligature  around  the 
vessel  to  be  tied,  may  be  made  by  pushing  the  point  of  a  darning 
needle  into  a  wooden  handle,  heating  the  eye  end  of  the  needle  red-hot 
and  bending  it  into  a  shallow  hook.  The  needle  can  be  threaded  with 


THE   PREPARATION  OF   MATERIAL.  285 

the  ligature,  which  may  then  be  easily  passed  around  the  vessel  in 
proper  position  for  tying. 

X.  How  to  inject  the  Catfish.  —  Anaesthetize  the  fish  by  placing  it 
in  a  small  quantity  of  water  to  which  a  little  chloroform  or  ether  has 
been  added.   As  soon  as  it  is  quiet,  cut  off  the  dorsal  spine.    Place  the 
fish  on  its  back,  and  open  the  body  cavity  by  a  median  ventral  slit. 
Continue  the  cut  forward   through  the  bones  of  the  pectoral  arch, 
taking  care  not  to  injure  the  internal  organs.     Separate  the  cut  edges 
by  pressing  down  on  both  pectoral  spines  at  once,  thus  disclosing  the 
heart  lying  in  its  pericardial  sac. 

In  a  specimen  intended  for  complete  dissection,  it  will  be  conven- 
ient to  inject  only  that  part  of  the  circulatory  system  which  carries 
venous  blood.  Before  the  blood  vessels  can  be  filled  with  the  injection 
mass,  they  must  be  emptied  of  their  contents.  To  get  the  blood  out, 
make  a  slit  with  fine  scissors  in  the  ventricle,  another  in  the  venous 
sinus,  another  in  each  of  the  veins  entering  the  liver  from  behind,  and 
another  in  the  vein  entering  each  kidney  from  behind.  Sop  up  all  the 
blood  that  can  be  induced  to  flow  from  these  incisions,  with  a  soft 
sponge  moistened  with  water,  or,  better,  with  normal  salt  solution, 
Then  inject.  Fill  the  syringe  with  the  injection  mass  well  shaken. 
Insert  its  cannula  into  the  arterial  bulb  through  the  slit  in  the  ven- 
tricle, ligature  the  nozzle  of  the  cannula,  and  inject  forward  to  fill  the 
branchial  aorta  and  its  branches.  Withdraw  the  cannula,  and  tighten 
the  ligature  to  prevent  the  escape  of  the  injection.  Insert  the  cannula 
in  turn  in  each  of  the  other  incisions,  ligature,  and  inject  backward. 
A  very  small  cannula  may  be  needed  for  injecting  the  veins  which 
return  the  blood  to  the  kidneys.  If  the  operation  be  properly  per- 
formed, the  arteries  (except  the  branchial)  may  be  recognized  in  dis- 
secting by  their  not  being  injected. 

XI.  How  to  inject  the  Frog  or  the  Turtle.  —  Anaesthetize  the  frog 
with  chloroform  or  ether.     Open  the  abdominal  cavity  by  a  median 
ventral  incision.  Continue  the  cut  forward  through  the  shoulder  girdle 
a  little  to  one  side  of  the  median  line.     Fasten  the  edges  of  the  cut 
apart,  and  disclose  the  heart.     With  sharp  scissors  snip  off  the.  point 
of  the  ventricle,  and  remove  the  blood  with  a  moist  sponge. 

The  arterial  system  of  the  frog  is  very  easily  injected.  Insert  the 
cannula  through  the  ventricle  into  the  base  of  the  arterial  trunk,  liga- 
ture, and  inject  forward.  Nothing  more  will  be  necessary  for  filling 
the  arterial  half  of  the  circulatory  system,  and  this  will  answer  our 
present  purpose. 

After  opening  the  body  of  the  turtle  as  directed  in  the  text  (p.  200), 
the  method  of  procedure  is  practically  the  same  as  for  the  frog. 


286  APPENDIX. 

XII.  How  to  inject  a  Sparrow.  —  After  anaesthetizing  the  sparrow 
with  chloroform,  the  heart  stops  very  quickly,  and  rapid  work  will  be 
necessary  to  find  it  still  beating  when  the  body  cavity  is  opened.     It 
should  be  beating  when  the  tip  of  the  ventricles  is  cut  off,  in  order 
that  as  much  blood  as  possible  may  be  removed  preparatory  to  a  good 
injection  of  the  arterial  system.     The  topography  of  the  skeleton 
should  be  first  studied  as  a  guide  to  removal  of  the  ventral  wall  of  the 
thorax. 

As  soon  as  the  sparrow  is  quiet,  make  a  transverse  cut  through  the 
abdominal  wall  behind  the  sternum,  and  a  longitudinal  cut  along  each 
side  of  the  thorax  through  the  sternal  ribs  and  coracoid.  Raise  the 
sternum,  open  the  pericardium,  and  snip  off  the  apex  of  the  ventricles 
with  sharp  scissors.  Sop  up  and  remove  the  blood  with  a  moist  sponge. 
Insert  a  small  cannula  through  the  right  ventricle  into  the  base  of 
the  pulmonary  artery,  ligature,  and  inject.  Insert  a  larger  cannula 
through  the  left  ventricle  into  the  base  of  the  aorta,  ligature  around 
the  ventricle,  and  inject. 

XIII.  How  to  inject  the  Rabbit.  —  Both  arteries  and  veins  should  be 
injected  in  the  rabbit,  but  with  different  colors.     Red  for  arteries,  and 
blue  for  veins,  are  most  commonly  used. 

The  more  quickly  the  blood  vessels  are  opened  after  administering 
chloroform,  the  better  in  general  will  be  the  results.  As  soon  as  the 
animal  is  quiet,  plunge  one  blade  of  a  pair  of  stout,  sharp-pointed 
scissors  through  the  abdominal  wall  in  the  wide  ventral  notch  between 
the  ribs.  Push  the  blade  forward  for  two  inches,  keeping  the  point  of 
it  close  under  the  ribs,  and  then  bring  the  blades  together,  making  a 
median  ventral  cut  through  the  sternum.  Draw  apart  the  edges  of  the 
cut,  slit  open  the  pericardium,  and  snip  off  the  apex  of  the  ventricles, 
and  make  a  slit  in  each  of  the  auricles.  Continue  the  ventral  cut 
posteriorly  for  two  inches  along  the  abdomen.  Turn  the  liver  for- 
ward, and  slit  open  the  portal  vein  where  it  enters  the  posterior  border 
of  the  liver. 

Cut  away  the  posterior  part  of  the  ventral  wall  of  the  thorax, 
and  by  liberal  use  of  a  moistened  sponge  assist  the  escape  of  the 
blood. 

1.  The  Arteries.     Inject  the  pulmonary  arteries  by  passing  a  small 
cannula  through  the  right  ventricle  into  their  base.    Inject  the  remain- 
ing arteries  through  a  larger  cannula  passed  through  the  left  ventricle 
into  the  base  of  the  aorta. 

2.  The  Veins.     Using  another  color,  inject  the  pulmonary  veins  by 
a  small  cannula  passed  through  the  left  auricle  into  their  base.     In- 
ject the  three  cavse  with  a  larger  cannula  passed  through  the  right 


THE  PREPARATION  OF  MATERIAL.  287 

auricle  into  their  bases.  Inject  the  portal  vein  and  its  branches 
through  a  small  cannula  posteriorly  directed  into  the  slit  previously 
made  to  let  out  the  blood. 

XIV.  On    Preparing    Skeletons.  —  The   cleaning  of  bones  is   not 
attractive  work,  but  it  is  made  comparatively  an  easy  matter  by  the 
process  described  below  (taken  from  Wilder  and  Gage's  "Anatomical 
Technology"),  and  the  intrinsic  value  for  study  of  the  disarticulated 
skeletons  thus  secured  makes  it  well  worth  while.     There  is  much 
that  can  be  learned,  too,  as  easily  in  the  preparation  of  a  skeleton 
as  in  any  other  way,  of  the  relations  of  the  bones  to  each  other  and 
to  the  muscles  and  tendons. 

The  "  liquid  soap  "  used  in  this  process  is  made  by  mixing  and 
liquefying :  — 

Rain  water 2000  cubic  centimeters. 

Strong  ammonia         .....          150  cubic  centimeters. 

Saltpeter 12  grams. 

White  soap  (hard) 75  grams. 

The  process  consists  in  (1)  removing  the  skin,  viscera,  and  the 
greater  part  of  the  muscles  from  the  skeleton ;  (2)  boiling  the  skele- 
ton for  forty  minutes  in  a  mixture  of  liquid  soap  one  part,  and  water 
four  parts;  (3)  boiling  the  skeleton  again  for  thirty  minutes  in  a 
mixture  of  equal  parts  of  liquid  soap  and  water;  and  (4)  cooling  the 
skeleton  by  immersing  in  cold  water,  and  cleaning,  rinsing,  and  dry- 
ing the  bones.  The  time  of  boiling  here  given  is  about  the  time 
required  in  the  preparation  of  a  rabbit  skeleton.  Less  time  will  be 
required  to  complete  the  boiling  of  smaller  skeletons. 

XV.  On  Cheap  Apparatus. — In  addition  to  the  pieces  of  simple  appa- 
ratus mentioned  in  the  text,  the  following  are  given  as  having  proved 
serviceable  :  — 

Dissecting  needles  may  be  made  by  pushing  with  pliers  the  eye  end 
of  common  sewing  needles  into  wooden  handles. 

A  simple  forceps,  which  the  author  has  often  preferred  to  use  in  the 
handling  of  minute  objects,  is  made  by  trimming  a  narrow  strip  of 
sheet  brass  or  tin  to  a  point  at  each  end,  and  bending  the  points  to- 
gether and  parallel. 

Bristles  of  the  ordinary  sort,  obtainable  from  a  harness  maker,  may 
be  tipped  with  paraffine  or  sealing  wax. 

Ordinary  earthenware  jars  of  several  gallons'  capacity  serve  well  as 
receptacles  for  organic  refuse  in  the  laboratory. 

A  serviceable  net  for  collecting  fresh-water  sponges  by  scraping  sub- 
merged timbers  is  made  by  attaching  a  circular  wire  frame  to  the  back 


288 


APPENDIX. 


of  a  common  garden  hoe,  and  suspending  a  bag  from  it,  so  as  to  collect 
the  material  loosened  by  the  blade  of  the  hoe. 

The  accompanying  cut  sufficiently 
_j?3^§^v\         explains  a  small  collecting  forceps  which 

Ois  useful  for  picking  live  bees,  wasps, 
cggggr\       and  the  like,  from  flowers.   The  frame 
~^S§sS£a      is  Of  wire.     The  blades  are  covered 
A  COLLECTING  FORCEPS.  witn  netting. 

The   water  net  figured  herewith  is 

made  of  a  loop  of  heavy  wire,  a  wooden  handle,  a  strip  of  muslin,  a 
shallow  bag  of  grasscloth  or  scrim 
or  other  netting,  and  some  small 
wire  for  binding  and  bracing.  The 
loop  of  wire  is  formed  as  shown  in 
the  figure :  the  crossed  ends  of  the 
wire  are  bent  at  right  angles  to  the 
plane  of  the  loop,  and  are  placed  in 
grooves  in  the  sides  of  one  end  of 
the  handle,  and  are  wrapped  there 
securely  with  smaller  wire.  Two 
grooves  are  filed  in  the  wire  of  the 
loop  at  different  points  for  the  secure 
attachment  of  the  braces,  as  shown 
in  the  figure.  The  narrow  band  of 
muslin  is  sewed  to  the  loop,  and  the 
netting  bag  to  the  muslin,  and  the  WATER  NET  :  a,  handle ;  6,  loop 

net  is  complete.     It  is  quickly  used,  of  wire  5  c>  completed  net,  side 

...  ,    ,  ,      i          i  view;  N,  completed  net,  from 

and  easily  cleaned  by  a  backward  above;    ^  brace;    e>  muslin 

push  through  the  water.  band ;  /,  netting  bottom. 


ACCENTUATED  LIST  OF  THE  TECHNICAL  TERMS  USED 
IN  THIS  BOOK,  TOGETHER  WITH  THEIR  ETYMOL- 
OGY AND  SYNONYMY. 

ab-do'-men  (Lat.  abdomen),  belly. 

ab-o'-ral  (Lat.  ab,  from,  and  os,  oris,  mouth). 

ac-e-tab'-u-lum  (Lat.  acetabulum,  vinegar  vessel?). 

ad-am-bu-la'-cral  (Lat.  ad,  to,  and  ambulacrum},  next  to  the  ambulacra. 

ad-duc'-tor  (Lat.  ad,  to  or  toward,  and  ducere,  to  draw). 

ad'-i-pose  (Lat.  adeps,  adiposus,  fat),  fatty. 

a-er-a'-tion  (Lat.  aer,  air),  exposure  to  air;  oxygenation. 


LIST  OF  TECHNICAL   TERMS.  289 

ag'-gre-gate  (Lat.  ad,  to  or  together,  and  gregare,  to  collect  into  a  flock), 
al-i-men'-ta-ry  (Lat.  alimentarius,  from  alere,  to  nourish), 
al'-u-let  (Lat.  alula,  dim.  of  a/a,  a  wing). 
am-bu-la'-crum,  pi.  ambulacra  (Lat.  ambulacrum,  an  alley), 
a-moe'-ba,  pi.  amcebas  (Gr.  amoibe,  a  change),  the  proteus  animalcule, 
a-mce'-boid  (Gr.  amoibe,  change,  and  eidos,  form),  like  the  amoeba, 
am-pul'-la,  pi.  ampullce  (Lat.  ampulla,  a  flask). 

a-nab'-o-lisrn  (Gr.  anabole,  something  heaped  up),  constructive  metab- 
olism; assimilation. 

an-aes'-the-tize  (Gr.  an,  privative,  and  aisthesis,  feeling  or  sensation), 
a'-nal  (Lat.  anus,  the  posterior  opening  of  the  alimentary  canal), 
a-nal'-o-gous  (Gr.  analogos,  according  to  due  ratio), 
an'-chy-lose  (Gr.  angkuloun,  to  stiffen),  fuse ;  coossify. 
an-i-mal'-cule  (Lat.  animal,  and  dim.  ule),  an  infusorian  ;  a  microscopic 

animal. 

an-ten'-na,  pi.  antennae,  (Lat.  antenna,  a  sail  yard),  the  feeler  of  an  insect, 
an-ten'-nule,  dim.  of  antenna. 

an-te-or'-bit-al  (Lat.  ante,  before,  and  orbis,  a  circle),  in  front  of  the  orbit, 
an-te'-ri-or  (Lat.  anterior,  cornp.  of  ante,  before),  fore ;  front, 
a'-nus  (Lat.  anus),  vent. 
a-or'-ta,  pi.  aortce  (Gr.  aorte). 
a'-pex  (Lat.  apex},  tip  or  point. 

a-quif'-er-ous  (Lat.  aqua,  water,  and/erre,  to  carry),  conducting  water. 
A-rach'-ni-da  (Gr.  arachne,  a  spider),  spiders, 
ar'-te-ry  (Lat.  arteria). 
Ar-throp'-o-da  (Gr.  arthron,  joint,  and  pous,  podos,  foot),  joint-footed 

animals. 

a-ryt'-e-noid  (Gr.  arutaina,  a  ladle,  and  eidos,  form), 
as-sim'-i-late  (Lat.  ad,  to,  and  simllare,  to  make  like),  to  convert  into 

a  like  substance. 
as-sim'-i-la-tion  (Lat.  assimilatio,  from  ad,  to,  and  similare,  to  make 

like),  anabolism;  constructive  metabolism, 
at'-las  (Gr.  Atlas,  the  god  who  bears  up  the  pillars  of  heaven),  first 

vertebra  of  the  neck,  sustaining  the  skull,  whence  the  name, 
at'-ro-phy  (Gr.  an,  privative,  and  trephein,  to  nourish),  a  wasting-away. 
au'-di-to-ry  (Lat.  auditorius,  from  audire,  to  hear),  pertaining  to  the 

sense  or  organs  of  hearing, 
au'-ri-cle  (Lat.  aura,  ear,  and  dim.  suffix). 
A'-ves  (Lat.  sing.  avist  a  bird),  birds, 
ax'-i-al  (Lat.  axis). 
ax'-il-lar  (Lat.  axilla,  armpit), 
bar'-bel  (Fr.  barbel,  dim.  of  Lat.  barbus,  a  beard)t 

19 


290  APPENDIX. 

bar'-bule  (Lat.  barbula,  dim.  of  barbus,  a  beard). 

ba-si-sphe'-noid  (compounded  of  basal  and  sphenoid,  q.v.). 

Ba-tra'-chi-a  (Gr.  batrachos,  a  frog),  amphibia. 

bi'-fid  (Lat.  bis,  twice,  and  Jindere,  fidi,  to  split),  cleft  or  parted. 

bi-fur'-ca-ted  (Lat.  bis,  twice,  and  Eng.  furcate,  forked). 

bi-lat'-er-al  (Lat.  bis,  twice,  and  latus,  side),  pertaining  to  two  sides. 

Bi-pin-na'-ri-a  (Lat.  bis,  twice,  and  pinna,  feather). 

bi-ro'-tu-late  (Lat.  bis,  twice,  and  rotula,  a  little  wheel). 

bi'-valve  (Lat.  bis,  twice,  and  valva,  valve). 

blas'-tu-la  (Gr.  blastos,  a  sprout). 

brach'-i-al  (Lat.  brachium,  arm),  pertaining  to  the  fore  limb. 

Brach-i-o-la'-ri-a  (Lat.  dim.  of  brachium,  arm,  and  -arid),  larva  of  a 

starfish. 

bran'-chi-al  (Lat.  branchia,  a  gill),  pertaining  to  the  branchiae  or  gills. 
bran-chi-os'-te-gal  (Gr.  brangchion,  gill,  and  stegein,  to  cover), 
bron'-chus,  pi.  bronchi  (Gr.  brongchos,  windpipe), 
buc'-cal  (Lat.  bucca,  cheek),  pertaining  to  the  mouth, 
cae'-cum,  pi.  cceca  (Lat.  ccecus,  blind), 
cal'-a-mus  (Lat.  calamus,  a  reed). 

cal-ca'-re-ous  (Lat.  calx,  lime),  containing  carbonate  of  lime, 
cap'-il-la-ry  (Lat.  capillus,  a  hair), 
car'-a-pace  (Fr.  carapace},  carapax ;  shell ;  shield, 
car'-di-nal  (Lat.  cardo,  a  hinge),  pertaining  to  the  hinge  in  the  shell 

of  Unio. 

ca-rot'-id  (Gr.  karos,  heavy  sleep), 
car'-po-met-a-car'-pus  (compounded  of   Gr.  karpos,  wrist,   and  meta- 

karpion,  beyond  the  wrist),  the  single  large  bone  of  the  bird's  hand, 

formed  by  the  coossification  of  carpal  and  metacarpal  bones, 
car'-pus  (Gr.  karpos,  wrist), 
car'-ti-lage  (Lat.  cartilago). 

cau'-dal  (Lat.  cauda,  tail),  pertaining  to  the  tail, 
cen'-trum,  pi.  centra  (Lat.  centrum),  the  body  of  a  vertebra, 
ce-phal'-ic  (Gr.  kephale,  head),  pertaining  to  the  head  or  brain, 
ceph-a-lo-tho'-rax  (Gr.  kephale,  head,  and  thorax,  the  chest). 
cer-e-bel'-lum  (Lat.  dim.  of  cerebrum,  the  brain), 
cer'-e-brum  (Lat.  cerebrum),  the  hemispheres  of  the  forebrain. 
cer'-vi-cal  (Lat.  cervix,  neck). 

chi-as'-ma  (Gr.  chiasma,  two  lines  placed  crosswise),  optic  commissure, 
chi'-tin  (Gr.  chiton,  a  corselet) . 

chlor'-a-gogue  (Gr.  chloros,  light  green,  and  agein,  to  lead), 
chrys'-a-lid,  pi.  chrysalids  >  (Gr>  cAnj^  gold)> 
chrys'-a-lis,  pi.  chrysalides  ) 


LIST  OF  TECHNICAL  TERMS.  291 

cil'-i-a  (Lat.  sing,  cilium,  an  eyelash). 

cir-cum-o'-ral  (Lat.  circum,  around,  and  os,  om,  mouth). 

cir-cum-val'-late  (Lat.  circumvallare,  to  surround  with  a  wall). 

clav'-i-cle  (Lat.  clavicula,  a  little  key),  the  collar  bone. 

cli-tel'-lum  (Lat.  clitellce,  a  pack  saddle). 

clo-a'-ca  (Lat.  cloaca,  a  sewer). 

co-a-lesce'  (Lat.  con,  with,  and  alescere,  to  grow  up),  unite;  fuse'  join. 

Cce-len-te-ra'-ta  (Gr.  koilos,  hollow,  and  enteron,  intestine). 

coe'-li-ac  (Gr.  koilia,  belly),  pertaining  to  the  abdomen. 

Co-le-op'-te-ra  (Gr.  koleon,  a  sheath,  and  pteron,  a  wing). 

col-u-mer-la  (Lat.  dim.  of  columen,  a  column) . 

com'-mis-sure  (Lat.  cominisura,  a  joining  together). 

con-cen'-tric  (Lat.  con,  together  with,  and  centrum,  center),  having  a 
common  center. 

con'-dyle  (Lat.  condylus,  from  Gr.  kondos,  a  head  or  knob). 

con-ju-ga'-tion  (Lat.  con,  together,  and  jungere,  to  join). 

con-tour'  (Fr.  contour,  outline). 

con-tract'-ile  (Lat.  con,  together,  and  trahere,  to  draw). 

cor'-a-coid  (Gr.  korax,  a  crow,  and  eidos,  form :  from  a  fancied  resem- 
blance of  the  human  coracoid  process  to  a  crow's  beak). 

cor'-ne-a  (Lat.  corneus,  horny). 

cor'-pus-cle  (Lat.  dim.  of  corpus,  body). 

cos'-ta  (Lat.  costa,  a  rib). 

cov'-erts  (Lat.  con,  with,  and  operire,  to  cover). 

cox'-a,  pi.  coxce  (Lat.  coxa,  the  hip). 

cra'-ni-um  (Gr.  kranion,  skull),  the  brain  case. 

cre-mas'-ter  (Gr.  kremaster,  a  suspender) . 

crib'-ri-form  (Lat.  cribrum,  a  sieve,  and  forma,  form). 

cri'-coid  (Gr.  krikos,  a  ring,  and  eidos,  form). 

cris'-sum  (Lat.  crisso,  to  move  the  haunches),  the  under  tail  coverts  of 
a  bird ;  feathers  around  the  cloaca. 

crys'-tal-line  (Lat.  crystallum;  Gr.  krustallos,  ice,  crystal). 

cu'-bi-tus  (Lat.  cubitus,  elbow). 

cul'-men  (Lat.  culmen,  from  celsus,  lofty). 

der'-mis  (Gr.  derma,  skin),  cutis. 

dex'-tral  (Gr.  dexiteros,  pertaining  to  the  right  hand) . 

di'-a-phragm  (Gr.  dia,  through,  and  phrassein,  to  fence  or  inclose). 

dif-fer-en-ti-a'-tion  (Lat.  dis,  apart,  audferre,  to  carry). 

di-gest'  (Lat.  digerere,  to  separate,  to  dissolve). 

dig'-it  (Lat.  digitus,  a  finger) . 

dig'-i-tate  (Lat.  digitus,  a  finger),  having  an  arrangement  like  that  of 
the  fingers  on  the  hand. 


292  APPENDIX. 

di-ce'-cious  (Gr.  dis,  twice,  and  oikos,  house),  having  the  two  sexual 
elements  produced  by  two  separate  individuals  of  the  same  species. 

Dip'-te-ra  (Gr.  dis,  two,  and  pteron,  a  wing). 

dis-ar-tic'-u-late  (Lat.  dis,  apart,  and  articulus,  dim.  of  artus,  a  joint), 
to  sunder;  to  separate  at  the  joint. 

dis-coid'-al  (Gr.  diskos,  a  round  plate,  and  eidos,  form),  disk-shaped. 

dis'-tal  (Lat.  distare,  to  stand  apart),  remote  from  the  point  of  attach- 
ment. 

di-ver-tic'-u-lum,  pi.  diverticula  (Lat.  diverticulum),  a  blind  tube  extend- 
ing outward  from  a  large  tube. 

dor'-sal  (Lat.  dorsum,  back),  tergal ;  opposed  to  ventral. 

du-o-de'-num  (Lat.  duodeni,  of  twelve  each :  the  human  duodenum  is 
in  length  about  equal  to  the  breadth  of  twelve  fingers,  hence  the 
name),  anterior  part  of  small  intestine. 

E-chi-no-der'-ma-ta  (Gr.  echinos,  sea  urchin,  and  derma,  skin). 

ec'-to-derm  (Gr.  ektos,  outside,  and  derma,  skin). 

ec'-to-sarc  (Gr.  ektos,  outside,  and  sarx,  flesh). 

e-gest'  (Lat.  e,  out,  and  gerere,  to  carry),  to  void. 

el'-y-tron,  el'-y-trum,  pi.  elytra  (Gr.  elutron,  a  sheath). 

em'-bry-o  (Lat.  embryo,  Gr.  embruon). 

em-bry-ol'-o-gy  (Gr.  embruon,  embryo,  and  logos,  a  discourse),  the 
study  of  the  development  of  embryos. 

en'-do-derm  (Gr.  entos,  within,  and  derma,  skin). 

en'-do-sarc  (Gr.  entos,  within,  and  sarx,  flesh) . 

en-do-skel'-e-ton  (Gr.  endon,  within,  and  skeleton,  a  dry  body). 

en-dos-mo'-sis  (Gr.  endon,  within,  and  osmos,  a  thrusting). 

en-to-mol'-o-gy  (Gr.  entomon,  an  insect,  and  logos,  a  discourse). 

ep-i-der'-mis  (Gr.  epi,  upon,  and  derma,  skin),  cuticle. 

ep-i-glot'-tis  (Gr.  epi,  upon,  and  glotta,  a  tongue). 

e-piph'-y-sis,  pi.  epiphyses  (Gr.  epi,  upon,  phuein,  to  grow). 

e-soph'-a-gus  (Gr.  oisophagos),  gullet. 

eth'-moid  (Gr.  ethmos,  a  sieve,  and  eidos,  form). 

Eu-sta'-chi-an,  discovered  by  Eustachius,  an  Italian  physician. 

ev-o-lu'-tion  (Lat.  evolvere,  to  roll  out  of,  to  unfold). 

ex-cre'-tion  (Lat.  excernere,  to  sift  out,  to  discharge). 

ex-o-skel'-e-ton  (Gr.  exo,  outside,  and  skeleton,  a  dry  body),  outside 
skeleton. 

ex-sert'-ed  (Lat.  exserere,  to  stretch  forth),  projecting  beyond  some 
other  part. 

ex-ten'-si-ble  (Lat.  ex,  out,  and  tendere,  to  stretch),  capable  of  being 
extended. 

ex-u'-vi-*,  pi.  exuviae  (Lat.  exuere,  to  draw  out,  to  pull  off). 


LIST  OF  TECHNICAL  TERMS.  293 

fac'-et  (Fr.  dim.  of  face). 

fau'-na  (Lat.  Fauni,  rural  deities),  the  animals  of  any  place  or  period 

taken  collectively. 
fem'-o-ral  (Lat./ewwr,  thigh), 
fe'-mur,  pi.  femora  (Lat.  femur),  thigh. 

fer-ti-li-za'-tion  (L&t.ferre,  to  bear),  fecundation;  impregnation, 
fib'-u-la,  pi.  fibulce  (Lat.  fibula,  that  which  binds  together;   named 

from  the  human  splint-like  fibula), 
fil'-a-ment  (L&t.filum,  a  thread), 
fil'-i-form  (L&t.jilum,  a  thread,  and/orwa,  form), 
fi'-lo-plume  (L&i.filum,  a  thread,  andpZwma,  a  soft  feather), 
floc'-cu-lar  (Lat.  flocculus,  dim.  oifloccus,  a  lock  of  wool), 
fo-li-a'-ta  (Lat.  from,  folium,  a  leaf), 
fo-ra'-men,  pi.  foram'ina  (Lat.  foramen,  a  perforation). 
fos'-sa,  pl.fossce  (Lat.  fossa,  a  pit,  from  fodere,  to  dig), 
fron'-tal  (Lat.  frontale,  an  ornament  for  the  forehead), 
fur'-cu-lum  (Lat.  furculum,  dim.  offurca,  a  fork),  wishbone, 
ga'-le-a,  pi.  galece  (Lat.  galea,  a  helmet). 

gan'-gli-on,  pi.  ganglia  (Lat.  ganglion,  Gr.  ganglion,  a  swelling), 
gas'-tric  (Gr.  gaster,  stomach). 

gas-troc-ne'-mi-us  (Gr.  gastroknemia,  calf  of  the  leg), 
gas-tros'-tege  (Gr.  gaster,  stomach,  and  siege,  roof), 
gem'-mule  (Lat.  dim.  of  gemma,  a  gem). 
gle'-noid  (Gr.  glene,  a  cavity,  and  eidos,  form), 
glo-chid'-i-um  (Gr.  glochis,  the  point  of  an  arrow), 
glot'-tis  (Gr.  from  glotta,  gldssa,  a  tongue), 
go'-nys  (Gr.  gonia,  an  angle), 
hal-te'-res  (Gr.  halter es,  dumb-bells),  balancers, 
ham'-u-li,  pi.  (Lat.  dim.  of  hamus,  a  hook), 
he'-mal  (Gr.  haima,  blood) 

He-mip'-te-ra  (Gr.  Jiemi,  half>  and  pteron,  a  wing),  bugs, 
hem'-i-sphere  (Gr.  hemi,  half,  and  sphaira,  a  sphere), 
hem'-o-lymph  (Gr.  haima,  blood,  and  lymph). 
he-pat'-ic  (Lat.  hepar,  the  liver), 
her-maph'-ro-dite  (Gr.  Hermaphroditos,  son  of  Hermes  and  Aphrodite 

[myth]),  being  of  both  sexes. 

Hex-ap'-o-da  (Gr.  hex,  six,  and  pous,  podos,  foot),  six-footed  insects, 
ho-mol'-o-gous  (Gr.  homologos,  agreeing). 
ho-mol'-o-gy  (Gr.  homologia,  agreement),  correspondence,  in  structure 

and  origin. 

hu'-me-rus  (Lat.  humerus*). 
hy'-dra,  Eng.  pi.  hydras  (Lat.  hydra,  water). 


294  APPENDIX. 

Hy-me-nop'-te-ra  (Gr.  Tinmen,  membrane,  and  pteron,  a  wing),  the  mem- 
brane-winged insects. 

hy'-oid  (Gr.,  the  letter  v,  and  eidos,  form). 

hy-pa-poph'-y-sis  (Gr.  hupo,  under,  and  apophusis,  a  process  of  a  bone). 

hy'-po-stome  (Gr.  hupo,  under,  and  stoma,  mouth). 

il'-i-o-sci-at'-ic  (compounded  of  ilium  and  sciatic,  q.v.). 

il'-i-um  (Lat.  ilia,  groin,  flank,  small  intestine). 

i-ma'-go  (Lat.  imago,  an  image),  the  perfect  insect ;  adult. 

in-ci'-sor  (Lat.  in,  in,  and  ccedere,  to  cut),  a  gnawing  tooth. 

in-fra-or'-bit-al  (Lat.  infra,  beneath,  and  orbis,  a  circle). 

in-fun-dib'-u-lum  (Lat.  infundibulum,  a  funnel). 

in-gest'  (Lat.  in,  in,  and  gerere,  to  bear  or  carry). 

in-glu'-vi-€s  (Lat.  ingluvies),  crop. 

in-nom'-i-nate  (Lat.  in,  not,  and  nominatus,  named). 

in'-sect  (Lat.  insectus,  from  insecare,  to  cut  in). 

in'-te-grate  (Lat.  integrare,  to  make  whole). 

in-ter-cos'-tal  (Lat.  inter,  between,  and  costa,  a  rib). 

in-ter-neu'-ral  (Lat.  inter,  between,  and  Gr.  neuron,  a  nerve),  between 
the  neurals. 

in-ter-or'-bit-al  (Lat.  inter,  between,  and  orbis,  a  circle),  between  the 
orbits. 

in-ter-pa-ri'-e-tal  (Lat.  inter,  between,  and  parietal,  q.v.). 

in-tes'-tine  (Lat.  intestinus,  from  intus,  the  inside). 

i'-ris  (Lat.  iris,  the  rainbow). 

is'-chi-um,  pi.  ischia  (Gr.  ischion,  the  hip  joint). 

isth'-mus  (Lat.  isthmus,  a  narrow  neck  of  land). 

i'-ter  (Lat.  iter),  a  passage. 

ju'-gal  (Lat.  jugum,  a  yoke). 

ju'-gu-lar  (Lat.  jugulum,  the  throat). 

ka-tab'-o-lism  (Gr.  kata,  down,  and  ballein,  to  throw),  destructive 
metabolism. 

la'-bi-al,  pertaining  to  the  lips. 

la'-bi-um  >  (Lat  laU       u  } 

la'-brum  ) 

lach'-ry-mal  (Lat.  lachryma,  a  tear). 

la-cin'-i-a  (Lat.  lacinia,  a  lappet  or  flap). 

lac'-te-al  (Lat.  lac,  lac t is,  milk). 

lar'-va  (Lat.  larva,  ghost,  specter). 

lar'-ynx  (Gr.  larungx,  the  larynx). 

lat'-er-al  (Lat.  latus,  side),  pertaining  to  the  side. 

Lep-i-dop'-te-ra  (Gr.  lepis,  a  scale,  and  pteron,  a  wing),  scaly-winged 
insects. 


LIST  OF  TECHNICAL  TERMS.  295 

lig'-a-ment  (Lat.  ligare,  to  bind). 

lig'-u-la  (dim.  of  Lat.  lingua,  a  tongue). 

lob'-u-late  (Gr.  lobos,  a  rounded  projection). 

lore  (Lat.  lorurn,  a  strap),  space  between  beak  and  eye  in  birds. 

lum'-bar  (Lat.  lumbus,  loin). 

mad'-re-po-rite  (Lat.  mater,  mother,  and  Gr.  poros,  a  soft  stone). 

mag'-num  (Lat.  magnus),  great. 

ma'-lar  (Lat.  mala,  the  cheek). 

Mal-pi'-ghi-an,  discovered  by  Malpighi. 

mam'-mal  (Lat.  mamma,  a  breast). 

Mam-ma'-li-a,  the  animals  which  nourish  their  young  with  milk. 

mam'-ma-ry  (Lat.  mamma,  a  breast,  a  glandular  organ  for  secreting 

milk),  pertaining  to  the  mammary  glands, 
man'-di-ble  (Lat.  mandere,  to  chew), 
man' -tie  (Lat.  mantellum,  a  cloth  or  cloak), 
ma-nu'-bri-um  (Lat.  from  manus,  hand), 
ma'-trix,  pi.  matrices  (Lat.  matrix,  mother), 
max-il'-la,  pi.  maxillce  (dim.  of  Lat.  mala,  a  jaw), 
max'-il-la-ry  (Lat.  maxilla,  a  little  jaw), 
max-il'-li-ped  (Lat.  maxilla,  jaw,  and  pes,  pedis,  foot), 
me-a'-tus  (Lat.  meare,  to  go),  a  passage. 
me'-di-an  (Lat.  medius,  middle), 
me-di-as-ti'-num  (Lat.  mediastinus  =  medius). 
me-dul'-la    (Lat.    medulla,    marrow),    the    hindbrain :    written    also 

medulla   oblongata. 

mes'-en-ter-y  (Gr.  mesos,  middle,  and  enteron,  intestine). 
mes-o-ster'-num  (Gr.  mesos,  middle,  and  sternon,  breast), 
mes-o-tho'-rax  (Gr.  mesos,  middle,  arid  thorax,  chest). 
me-tab'-o-lism  (Gr.  metabole,  change),  the  constructive   and  destruc- 
tive changes  which  take  place  within  the  cell,  a  process  known 

only  through  its  results. 

met-a-car'-pus  (Gr.  meta,  beyond,  and  Jcarpos,  wrist). 
met-a-mor'-pho-sis,  pi.  metamorphoses   (Gr.   meta,   beyond,   over,   and 

morphe,  form,  shape),  the  structural  changes  which  take  place 

in  an  animal  after  it  emerges  from  the  egg. 
met-a-no'-tum  (Gr.  meta,  beyond,  hind,  and  notos,  back), 
met-a-ster'-num  (Gr.  meta,  beyond,  and  sternon,  breast), 
me-tas'-to-ma  (Gr.  meta,  behind,  and  stoma,  mouth), 
met-a-tar'-sus  (Gr.  meta,  beyond,  and  tarsos,  tarsus), 
met-a-tho'-rax  (Gr.  meta,  beyond,  and  thorax,  chest). 
met-a-zo'-an  (Gr.  meta,  beyond,  and  zoon,  animal),  one  of  the  "higher" 

animals ;  any  animal,  not  a  protozoan ;  a  many-celled  animal. 


296  APPENDIX. 

mo'-lar  (Lat.  molere,  to  grind),  a  grinding  tooth. 

Mol-lus'-ca  (Lat.  mollis,  soft),  mollusks. 

mo'-tile  (Lat.  movere),  having  power  of  motion. 

mu'-cous  (Lat.  mucus,  mucus). 

Myr-i-ap'-o-da  (Gr.  murios,  numberless,  and  pous,  podos,  foot). 

na'-sal  (Lat.  nasus,  the  nose),  pertaining  to  the  nose. 

ne-phrid'-i-a  (Gr.  nephros,  kidney). 

neu'-ral  (Gr.  neuron,  a  nerve),  pertaining  to  the  nervous  system  or  some 
part  of  it. 

nic'-ti-tat-ing  (Lat.  nictare,  to  wink). 

no'-dus  (Lat.  nodus,  a  knot). 

no'-tum  (Gr.  notos,  back). 

nu'-chal  (Lat.  nucha,  the  nape). 

nu'-cle-us  (Lat.  dim.  of  nux,  nucis,  a  nut). 

nymph  (Lat.  Nympha  [myth.] ,  goddess  of  meadows,  waters,  forests,  etc.). 

ob'-tu-ra-tor  (Lat.  obturare,  to  stop  up). 

oc'-ci-put  (Lat.  ob,  against  or  back  of,  and  caput,  head). 

o-cel'-lus,  pi.  ocelli  (Lat.  dim.  of  oculus,  eye). 

oc-u-lo-mo'-tor  (Lat.  oculus,  the  eye,  and  movere,  to  move). 

O-don'-a-ta  (Gr.  odous,  odontos,  a  tooth). 

o-don'-toid  (Gr.  odous,  a  tooth,  and  eidos,  form). 

o-lec'-ra-non  (Gr.  olene,  elbow,  and  kranion,  head). 

ol-fac'-to-ry  (Lat.  olere,  to  smell,  and  facere,  to  make),  pertaining  to 
the  sense  of  smell. 

o-mo-s'ter'-num  (Gr.  omos,  shoulder,  and  sternon,  breast). 

o'-b'-sperm  (Gr.  don,  egg,  and  sperma,  seed),  the  fertilized  ovum. 

o-per'-cu-lum  (Lat.  from  operire,  to  cover). 

op'-tic  (Gr.  optikos,  belonging  to  sight),  pertaining  to  the  eye. 

o'-ral  (Lat.  os,  oris,  mouth),  pertaining  to  the  mouth. 

or'-bit  (Lat.  orbis,  a  circle). 

or'-i-fice  (Lat.  os,  mouth,  and  facere,  to  make). 

Or-thop'-te-ra  (Gr.  orthos,  straight,  and  pteron,  a  wing),  the  straight- 
winged  insects. 

os  cru'-ris  (Lat.  os,  bone,  and  cruris,  leg). 

os-mo'-sis  (Gr.  osmos,  impulse). 

os'-si-fy  (Lat.  os,  ossis,  a  bone),  to  become  bone. 

os'-si-cle  (Lat.  dim.  of  os,  a  bone),  a  little  bone. 

os'-te-ole  (Lat.  dim.  of  ostium,  mouth). 

os-te-ol'-o-gy  (Gr.  osteon,  bone,  and  logos,  discourse). 

o'-va-ry  (Lat.  ovarium,  from  ovum,  egg). 

o'-vate  (Lat.  ovum,  egg),  egg-shaped. 

o'-vi-duct  (Lat.  ovum,  egg,  and  ductus,  duct,  tube). 


LIST   OF  TECHNICAL  TERMS.  297 

o-vi-pos'-i-tor  (Lat.  ovum,  egg,  audponere,  to  place). 

o'-vum  (Lat.  ovum),  egg. 

pal'-ate  (Lat.  palatum),  the  roof  of  the  mouth. 

pal'-a-tine  (Lat.  palatum,  the  roof  of  the  mouth),  the  bones  supporting 

the  palate. 

pal'-li-al  (Lat.  pallium,  a  mantle), 
pal'-pus,  pi.  palpi  (Lat.  palpus),  feeler. 

pan'-cre-as  (Gr.  pangkreas,  pancreas,  from  pas,  all,  and  kreas,  flesh), 
pa-pil'-la,  pi.  papillce  (Lat.  papilla),  a  pimple-like  projection, 
par-a-me'-ci-um  (Gr.  para,  beside,  and  mekos,  strength). 
par-a-sphe'-noid  (Gr.  para,  beside,  and  sphenoid,  q.v.). 
pa-ri'-e-tal  (Lat.  paries,  a  wall), 
pa-rot'-id  (Gr.  para,  beside,  and  ous,  otos,  the  ear), 
pa-tel'-la  (Lat.  dim.  of  patena,  a  pan),  the  kneepan. 
pec'-ti-na-ted  (Lat.  pecten,  a  comb),  toothed,  like  a  comb, 
pec'-to-ral  (Lat.  pectus,  breast),  pertaining  to  the  breast. 
ped'-i-cel  (Lat.  pediculus,  dim.  of  pes,  pedis,  foot), 
ped-i-cel-la'-ri-a,  pi.  pedicellarice  (Lat.  pedicellus,  pedicel,  and  -aria). 
pel'-vis  (Lat.  pelvis,  a  basin). 

per-i-car'-di-um  (Gr.  peri,  around,  and  kardia,  the  heart), 
per'-i-stome  (Gr.  peri,  around,  and  stoma,  mouth), 
per-i-to-ne'-um  (Gr.  peri,  around,  and  teinein,  to  stretch), 
pha-lan'-ges,  pi.  of  phalanx  (Gr.  phalangx,  phalanx), 
phar'-ynx  (Gr.  pharungx). 
pi'-ne-al  (Lat.  pinea,  the  cone  of  a  pine). 
Pis'-ces  (Lat.  pi.  of  piscis,  a  fish),  fishes, 
pi-tu'-i-ta-ry  (Lat.  pituita,  phlegm,   mucus).     This  body  was  once 

erroneously  supposed  to  secrete  the  mucus  of  the  nostrils, 
plas'-ma  (Gr.  plasma). 
plas'-tron  (Fr.  plastron,  a  breastplate). 
pleu'-rum,  pi.  pleura  (Gr.  pleura,  the  side), 
plex'-us  (Lat. plexus),  a  twining  or  twisting;  a  network, 
por'-tal  (Lat.  porta,  a  gate),  the  gateway  of  the  liver,  the  portal  vein, 
post'-ca-va,  pi.  postcavce  (Lat.  post,  after,  and  cavus,  hollow),  posterior 

vena  cava  or  ascending  vena  cava. 
pos-te'-ri-or  (Lat.  comp.  of  posterns,  coming  after),  hinder  ;  opposed  to 

anterior. 

post-or'-bit-al  (Lat.  post,  after  or  behind,  and  orbis,  a  circle), 
prae'-ca-va,  pi.  prcecavce  (Lat.  prce,  before,  and  cavus,  hollow),  anterior 

vena  cava  or  descending  vena  cava. 
pre-cor'-a-coid  (Lat.  pro?,  before,  and  coracoid,  q.v.). 
pre-max'-il-la-rv  ( Lat.  vrce,  before,  and  maxilla,  jaw). 


298  APPENDIX. 

pre-o-per'-cu-lum  (Lat.  prce,  before,  and  operculum,  a  covering). 

pre-sphe'-noid  (Lat.  prce,  before,  and  sphenoid,  q.v.). 

pri'-ma-ries  (Lat.  primus,  the  first). 

pro-bos'-cis,  pi.  probos'cides  (Gr.  pro,  before,  and  boskein,  to  feed). 

pro-neph'-ros  (Gr. pro,  before,  and  nephros,  kidney). 

pro-no'-tum  (Gr.  pro,  before,  and  notos,  back). 

pro-6'-tic  (Gr.  pro,  before,  and  ous,  otos,  ear). 

pro-ster'-num  (Gr.  pro,  before,  and  sternon,  breast). 

pro-sto'-mi-um  (Gr.  pro,  before,  and  stoma,  mouth). 

pro-tho'-rax  (Gr.  pro,  before,  and  thorax,  thorax). 

pro'-to-plasm  (Gr.  protos,  first,  and  plasma,  form). 

Pro-to-zo'-a  (Gr.  protos,  first,  and  zoon,  animal). 

pro-tract'-or  (Lat.  pro,  forward,  and  trahere,  to  draw). 

pro-ven-tric'-u-lus  (Lat.  pro,  forward,  and  ventriculus,  stomach). 

prox'-i-mal  (Lat.  proximus,  nearest),  nearest  the  point  of  attachment, 
or  nearest  the  median  point  or  plane. 

pseu-do-po'-di-a  (Gr.pseudes,  false,  and  pous,  podos,  foot),  false  feet. 

pter-o-stig'-ma  (Gr.  pteron,  a  wing,  and  stigma,  a  spot). 

pter'-y-goid  (Gr.  pterux,  a  wing,  and  eidos,  form). 

pu'-bis,  pi.  pubes  (Lat.  pubis). 

pul-mo-cu-ta'-ne-ous  (Lat.  pulmo,  a  lung,  and  Eng.  cutaneous,  pertaining 
to  the  skin). 

pul'-mo-na-ry  (Lat.  pulmo,  lung),  pertaining  to  the  lungs. 

pul-vil'-lus,  pi.  pulvilli  (Lat.  pulvillus),  a  little  cushion. 

pu'-pa,  pi.  pupce  (Lat.  pupa,  a  doll,  a  puppet). 

pu'-pil  (Lat.  pupilla,  originally  dim.  of  pupa,  a  girl),  the  circular  open- 
ing through  the  iris. 

py'-gal  (Gr.  puge,  the  rump). 

py'-go-style  (Gr.  puge,  rump,  and  stulos,  a  pillar  or  stylet  for  writing). 

py-lo'-rus  (Lat.  pylorus,  a  gatekeeper). 

quad'-rate  (Lat.  quadratum,  quadrangular). 

ra'-di-us,  pi.  radii  (Lat.  radius,  a  staff  or  rod). 

rad'-u-la,  pi.  radulce  (Lat.  radula,  a  scraper,  from  radere,  to  scrape) . 

ra'-mus,  pi.  rami  (Lat.  ramus,  a  branch). 

rec'-tri-ces  (pi.  of  Lat.  rectrix,  a  governess),  tail  feathers. 

re'-nal  (Lat.  renes,  the  kidneys),  pertaining  to  the  kidneys. 

Rep-til'-i-a  (Lat.  reptilis,  from,  repere,  to  creep),  reptiles. 

re-tract'-or  (Lat.  re,  back,  and  trahere,  to  draw). 

re-trorse'  (Lat.  retro,  back,  and  vertere,  to  turn). 

rha'-chis  (Gr.  rachis,  a  dorsal  ridge  or  spine),  shaft. 

ric'-tus  (Lat.  ringi,  rictus,  to  open  wide  the  mouth),  the  gape. 

ros'-trum  (Lat.  rostrum,  a  beak). 


LIST  OF   TECHNICAL  TERMS.  299 

sac'-cu-la-ted  (^Lat.  sacculus,  dim.  of  saccus,  a  sack),  bearing  little  sacs. 
sa'-crum,  the  Latin  name  for  the  anchylosed  human  sacral  vertebrae, 
sal'-i-va-ry  (Lat.  saliva,  spittle),  pertaining  to  the  saliva, 
sar'-code  (Gr.  sarx,  flesh,  and  eidos,  form). 

scap'-u-la,  pi.  scapulce  (Lat.  scapula},  shoulder  blade. 

sci-at'-ic  (Lat.  sciaticus),  pertaining  to  the  hip. 

scle-rot'-ic  (Gr.  skleros,  hard). 

scu-tel'-la,  pi.  scutellce  (Lat.  fem.  dim.  of  scutum,  a  shield). 

scu'-tel-late  (Lat.  scutella,  a  dish  or  plate),  covered  with  scutella,  over- 
lapping plate-like  scales. 

sec'-ond-a-ries,  pi.  of  secondary  (Lat.  secundarius,  second). 

seg-men-ta' -tion  (Lat.  segmentum,  segment,  from  secare,  to  cut). 

seg'-ment  (Lat.  segmentum,  from  secare,  to  cut  off),  somite ;  ring ;  joint. 

sep'-tum,  pi.  septa  (Lat.  septum,  a  fence  or  partition),  a  partition. 

ser'-ra-ted  (Lat.  serra,  a  saw),  toothed,  like  a  saw. 

ses'-a-moid  (Gr.  sesamon,  a  kind  of  seed,  and  eidos,  form),  seedlike  (?) 
bones  formed  in  the  tendons. 

ses'-sile  (Lat.  sessum,  seated,  from  sedere,  to  sit). 

se'-ta,  pi.  setce  (Lat.  seta),  a  bristle. 

sin'-is-tral  (Lat.  sinister,  the  left  hand),  pertaining  to  the  left-hand 
side ;  turning  toward  the  left. 

si'-nus,  Eng.  pi.  sinuses  (Lat.  sinus),  a  curve ;  a  hollow. 

si'-phon  (Lat.  sipho,  Gr.  siphon,  a  bent  tube  for  the  transference  of 
water). 

skel'-e-ton  (Gr.  skeleton,  a  dried  body). 

sperm  (Lat.  sperma,  seed),  spermatozoa ;  the  male  reproductive  element. 

sper'-ma-ry  (Lat.  sperma,  seed),  testicle. 

sper-mat'-ic  (Lat.  spermaticus,  pertaining  to  spermatic  fluid). 

sphe'-noid  (Gr.  sphen,  a  wedge,  and  eidos,  form). 

spic'-ule  (Lat.  dim.  of  spica,  a  dart). 

spir'-a-cle  (Lat.  spirare,  to  breathe). 

spleen  (Gr.  splen}. 

spu'-ri-ous  (Lat.  spurius),  false;  whence  the  spurious  quills  constitute 
what  is  sometimes  called  the  "  false  wing." 

squa-mo'-sal  (Lat.  squama,  a  scale). 

ster'-num  (Lat.  from  Gr.  sternon,  breast). 

stri'-a-ted  (Lat.  stria,  a  channel),  marked  with  fine  grooves  or  lines. 

strid-u-la'-tion  (Lat.  stridulare,  to  creak). 

sty'-let  (Lat.  stylus,  a  style  [writing  instrument]). 

sub-cla'-vi-an  (Lat.  sub,  under,  and  clavicle,  a  little  key),  beneath  the 
clavicle. 

sub-cos' -tal  (Lat.  sub,  under,  and  costa,  a  rib). 


300  APPENDIX. 

sub-gen'-i-tal  (Lat.  sub,  under,  and  genitalis,  the  genital  organs), 
sub-lin'-gual  (Lat.  sub,  under,  and  lingua,  a  tongue), 
sub-max'-il-la-ry  (Lat.  sub,  under,  and  maxilla,  a  jaw), 
sub-me'-di-an  (Lat.  sub,  under,  and  medius,  the  middle), 
sub-quad'-rate  (Lat.  sub,  under,  and  quadratum,  quadrangular),  some. 

what  four-angled. 

suc-to'-ri-al  (Lat.  sugere,  suctum,  to  suck),  adapted  for  sucking, 
su'-ture  (Lat.  sutura,  a  seam), 
swim'-mer-et,  abdominal  swimming  appendage, 
sym'-phy-sis  (Gr.  sumphuein,  to  grow  together),  coalescence;  fusion-, 

coossification. 

syr'-inx  (Gr.  suringx,  a  pipe), 
tac'-tile  (Lat.  tangere,  tactum,  to  touch), 
tar'-so-met-a-tar'-sus  (compounded  of  tarsus  and  metatarsus;  the  name 

for  the  single  bone  formed  by  the  fusion  of  these), 
tar'-sus,  pi.  tarsi  (Gr.  tarsos,  the  flat  of  the  foot), 
teg'-mi-na  (Lat.  pi.  of  legmen,  from  tegere,  tectum,  to  cover), 
tel'-son  (Gr.  telson,  a  limit),  the  terminal  joint  of  the  abdomen  of 

Crustacea. 

ten'-don  (Lat.  lendere,  to  stretch), 
te-nac'-u-lum  (Lat.  tenere,  to  hold), 
ten'-ta-cle  (Lat.  tentare,  to  feel). 
ter'-gum,  pi.  terga  (Lat.  tergu?n),  back, 
ter'-mi-nal  (Lat.  terminare,  to  put  an  end  to),  on  the  end. 
ter'-ti-a-ries,  pi.  of  tertiary  (Lat.  tertius,  the  third), 
tes'-tis,  pi.  testes  (Lat.  testis),  spermary. 
tho-rac'-ic,  pertaining  to  the  thorax, 
tho'-rax  (Gr.  thorax,  the  chest), 
thy'-mus  (Gr.  thumos). 

thy'-roid  (Gr.  thureos,  a  shield,  and  eidos,  form), 
tib'-i-a,  pi.  tibiae  (Lat.  tibia,  the  shin  bone,  also  a  pipe  or  flute  which 

was  originally  made  of  bone). 
tra'-che-a,  pi.  tracheae,  (Lat.  trachea},  the  windpipe ;  also  air  tubes  of 

insects. 

trans-verse'  (Lat.  trans,  across,  and  vertere,  to  turn),  across  the  long  axis. 
tri-gem'-i-nal  (Lat.  tri,  three,  and  geminus,  a  twin), 
tri-un'-gu-lin  (Lat.  tri,  three,  and  unguis,  a  claw), 
tro-chan'-ter  (Gr.  trochanter,  a  runner), 
trun'-ca-ted  (Lat.  truncare,  to  cut  short),  appearing  as  if  cut  off  squarely 

at  the  tip. 
tu'-ber-cle  (Lat.  tuber,  from  tumere,  to  swell,  and  dim.  cle,  little),  a 

small  knob-like  prominence. 


LIST  OF   TECHNICAL   TERMS.  301 

tur'-bi-nal  (Lat.  turbo,  a  top). 

tym'-pa-num,  pi.  tympani  (Lat.  tympanum,  a  drum  head). 

typ'-i-cal  (Lat.  typicus),  expressing  the  essential  characteristics  of  a 

type. 

ul'-na  (Lat.  ulna,  the  elbow), 
um-bi-li'-cus  (Lat.  umbilicus,  the  navel),  an  opening  into  the  calamus 

of  a  feather. 

um'-bo,  pi.  umbo'nes  (Lat.  umbo),  a  boss  or  short  beak, 
un'-ci-nate  (Lat.  uncus,  a  hook). 

u-ni-cel'-lu-lar  (Lat.  unus,  one,  and  cella,  a  cell),  one-celled, 
u'-ni-valve  (Lat.  unus,  one,  and  valva,  fold), 
u-re'-ter  (Gr.  ouron,  urine). 

u'-ri-na-ry  (Lat.  urina,  urine),  pertaining  to  the  urine, 
u'-ro-stege  (Gr.  oura,  tail,  and  stege,  roof). 
u'-ro-style  (Gr.  oura,  tail,   arid  stulos,  pillar,   style    [for  writing]),  a 

styliform  process   at  the   posterior  extremity  of  the  vertebral 

column. 

u'-te-rus  (Lat.  uterus),  the  womb, 
vac'-u-ole  (Lat.  vacuus,  empty). 

va'-gus  (Lat.  vagus,  wandering,  called  also  the  pneumo-gastric  nerve), 
vane  (O.  Eng.fane,  a  weathercock). 

vas'-cu-lar  (Lat.  vasculum,  dim.  of  vas,  a  vessel),  containing  vessels. 
vein  (Lat.  vena)  :   veinule  and  veinlet  are  its  diminutives, 
ven'-tral  (Lat.  venter,  the  belly). 
ven'-tri-cle  (Lat.  ventriculus,  dim.  of  venter). 
ver'-mi-form  (Lat.  vermis,  a  worm,  and  forma,  form),  shaped  like  a 

worm. 

ver'-te-bra,  pi.  vertebra  (Lat.  vertere,  to  turn), 
ves'-i-cle  (Lat.  vesicula,  dim.  of  vesica,  a  bladder),  a  cyst, 
ves'-ti-bule  (Lat.  vestibulum,  a  place  of  entrance), 
vis'-ce-ra  (Lat.  pi.  of  viscus),  the  entrails ;  internal  organs, 
vo'-mer  (Lat.  vomer). 

xiph-i-ster'-num  (Gr.  xiphos,  a  sword,  and  sternum,  q.v.). 
xiph'-oid  (Gr.  xiphos,  a  sword,  and  eidos,  form), 
zyg-a-poph'-y-sis,  pi.  zygapophyses  (Gr.  zungon,  a  yoke,  and  apophysis, 

process  of  a  bone),  one  of  the  articular  processes  of  a  vertebra. 


302  APPENDIX. 


SUGGESTIONS  TO  THE  TEACHER. 

Some  knowledge  of  the  difficulties  encountered  by  one  who  \vould 
attempt  a  well-balanced  elementary  courso  in  zoology,  in  some  of  our 
secondary  schools  at  the  present  time,  prompts  this  final  word  to  the 
teacher. 

I  would  recommend  the  teacher,  first  of  all,  to  note  the  amount  of 
work  outlined  in  the  foregoing  pages,  and  to  consider  whether  it  may 
all  be  done  in  the  time  at  the  disposal  of  his  class.  Having  often 
found  that  a  particular  animal,  when  wanted  alive  for  study,  is  not  to 
be  had,  I  have  mentioned  several  types  to  which  each  outline  may  be 
applied,  and  have  perhaps  added  more  outlines  in  brief  than  so  ele- 
mentary a  course  requires ;  yet  I  trust  the  advantage  of  this  will  be 
apparent  when  selections  are  to  be  made.  For  a  short  course  it  might 
be  more  profitable  to  study  only  the  part  relating  to  insects  or  the  part 
relating  to  vertebrates,  rather  than  to  attempt  to  "  go  through  "  the 
book. 

I  would  suggest  that  the  teacher  arrange  his  work  so  as  to  have 
an  hour  of  freedom  from  teaching  preceding  the  hour  for  zoology, 
which  may  be  spent  in  preparing  for  the  recitation.  The  hour  will  be 
anything  but  vacant  if  devoted  to  the  preparation  for  the  hour  to 
follow  it. 

I  would  suggest  that  the  teacher  spend  the  first  hour  of  the  session 
in  familiarizing  his  pupils  with  the  microscope,  —  with  its  parts  and 
their  use.  I  would  give  them  each  a  slide  with  some  object  of  simple 
outlines  mounted  on  it,  and  instruct  them  in  moving  the  object  into 
the  field,  in  finding  it  with  low  and  with  high  powers,  and  I  would 
require  an  outline  drawing  of  it. 

Then  I  would  proceed  at  once  to  the  study  of  amoeba,  paramecium, 
sponge,  and  hydra,  passing  over  this  part  as  rapidly  as  proved  consis- 
tent with  the  mastering  of  the  fundamental  ideas  of  zoology  which 
these  types  are  well  adapted  to  introduce.  For  this  part  of  the  study, 
I  would  provide  all  the  material,  and  present  it  as  demonstrations, 
requiring  of  the  pupils  only  that  they  study  it  and  make  drawings 
showing  all  they  are  able  to  make  out,  naming  the  parts  and  explain- 
ing their  action ;  and  that  they  make  note  of  the  habits  and  habitat 
of  these  animals. 

Then  I  would  begin,  as  early  as  possible  in  the  term  (all  the  mate- 
rial of  this  book  is  arranged  with  reference  to  beginning  the  course 
in  early  autumn),  the  study  of  insects.  And  for  the  remainder  of  the 


SUGGESTIONS  TO   THE   TEACHER.  303 

course  I  would  require  that  all  the  work  outlined  in  the  text  be  done 
by  the  student,  and  that  the  greater  part  of  it  be  done  by  each  student 
for  every  animal  studied.  Just  how  much  dissecting  and  how  much 
field  work,  etc.,  should  be  required,  will  have  to  be  determined  in 
accordance  with  the  abilities  and  needs  of  individual  classes.  Some 
of  the  larger  dissections  may  be  made  as  demonstrations  by  the 
teacher  or  assistants ;  but  I  consider  it  absolutely  necessary  that  each 
student  should  study  the  structure  of  every  type,  and  record  his 
observations  in  some  permanent  form,  notes,  drawings,  or  preparations 
of  illustrative  material.  While  freely  acknowledging  the  great  value 
of  original  drawings,  however  crude,  I  think  it  should  be  borne  in 
mind  that  the  student  who  has  no  aptitude  for  this  art  may  find 
continual  drawing  as  irksome  as  it  is  unsatisfactory  to  him.  I  have 
found  students,  wholly  incapable  of  making  a  presentable  drawing, 
able  to  make  beautiful  preparations  of  material  for  demonstrations 
and  for  collections.  The  true  ends  of  scientific  instruction  will  not 
be  promoted  by  keeping  any  student  long  at  work  which  he  cannot 
make  pleasant  or  satisfactory. 

The  field  work  suggested  in  this  book  forms  an  important  feature 
of  it,  yet  not  so  important,  I  am  persuaded,  as  it  should  be  made. 
I  would  require  of  the  students,  that,  in  so  far  as  is  possible,  they 
collect  all  their  own  material  for  study.  The  observations  made 
while  doing  this  will  not  be  among  the  least  valuable  things  learned 
about  animals  in  the  course.  And  I  would  not  discourage  the  collection 
of  cabinet  specimens.  This  has  its  place.  There  is  one  benefit  to  be 
had  from  a  thorough  study  of  types,  and  there  is  another  benefit  to 
be  had  from  personal  contact  with  nature  in  a  great  variety  of  forms. 
I  would  go  out  with  the  students  often,  and  direct  their  observations 
in  the  field.  Making  use  of  the  haunts  of  animals  most  accessible 
for  study,  I  would  assign  simple  tasks  of  outdoor  observation,  requir- 
ing little  time,  and  I  would  not  limit  these  to  observations  on  the 
types  studied  in  the  course.  Many  a  teacher  neglects  abundant  oppor- 
tunity for  doing  this.  Material  for  such  study  is  at  the  very  doors  of 
a  majority  of  the  schools  in  which  elementary  zoology  is  taught.  Our 
higher  institutions  of  learning,  located  often  in  the  heart  of  great 
cities,  by  establishing  seaside  and  lakeside  laboratories,  get,  at  a  great 
expenditure  of  time  and  money,  that  which  the  secondary  schools 
may  have  if  they  choose,  without  expense,  as  a  part  of  their  daily  life. 
And  who  shall  say  that  the  study  of  animals  in  their  relation  to  nature 
is  of  more  worth  in  one  school  or  in  the  other  ? 

I  urge  as  most  important,  that  the  teacher  maintain  strictest  super- 
vision of  all  work,  that  there  may  be  no  idling  in  the  field,  no  smat- 


304  APPENDIX. 

tering  in  the  laboratory,  and  as  little  as  may  be  of  memorized 
second-hand  information  in  the  classroom.  Definite  results  should 
be  required  of  every  excursion  made  by  students  to  the  field.  Quiet, 
careful,  and  diligent  work  should  be  insisted  on  in  the  laboratory. 
Scrupulous  neatness  should  be  maintained.  Every  student  should  be 
required  to  keep  his  table  clean  and  his  specimens  fresh,  and  to 
entirely  remove  from  the  laboratory  all  materials  in  his  charge  that 
are  liable  to  become  offensive. 

Lastly  I  would  urge  the  teacher  to  acquaint  himself  with  the  entire 
fauna  of  his  own  locality.  Doubtless  in  many  localities  other  types 
than  those  mentioned  in  this  book  are  better  and  more  available  for 
study:  such  he  is  recommended  to  find  and  use  by  his  friend  and 
fellow-worker, 

THE  AUTHOR. 


INDEX. 


Abdomen,  of  asellus,  125. 

of  back-swimmer,  62. 

of  beetle,  76. 

of  bumblebee,  65. 

of  butterfly,  42. 

of  cicada,  60. 

of  crawfish,  114. 

of  cyclops,  127. 

of  dragon  fly,  45. 

of  fly,  83. 

of  grasshopper,  51. 

of  mussel,  145. 

of  pupa,  92. 

of  rabbit,  243. 

of  sparrow,  216,  221. 

of  spider,  108. 

Acridium.     See  Schistocera. 
Air  sac  of  snail,  156. 
Alimentary  canal.     See  Digestive 

organs. 

Amoeba,  12,  278. 
Amoeboid  blood,  137. 
Analogy,  45. 
Anasa,  57. 
Antenna,  of  crustacean,  118, 125, 127. 

of  insect,  39. 

Antennule,  118,  125,  127. 
Aorta.     See  Arteries. 
Aperture.     See  Sponge  gemmules. 
Arachnida,  105-109. 
Arm  bones,  of  frog,  192. 

of  rabbit,  257. 

of  turtle,  206. 
Arteries,  of  crawfish,  119. 

of  fish,  163,  168. 

of  frog,  182,  184. 

of  mussel,  146. 

of  rabbit,  247. 

of  sparrow,  226. 

of  turtle,  202. 
Arthropoda,  128. 
Asellus,  125. 
Asilus,  85. 


Asterias,  266,  267. 
Aves,  211. 

Backbone.     See  Spinal  column. 

Back-swimmer,  61. 

Barbels,  162. 

Batrachia,  178,  198. 

Beak,  215. 

Bee  killer,  85. 

Beetle,  74. 

blister,  74. 

Harpalus,  78. 

larvse,  79. 

locust  borer,  78. 

red  milkweed,  78, 

soldier,  77. 

whirligig,  79. 
Birds,  211,  236. 
Blastula,  159. 
Blood,  of  fish,  163. 

of  insects,  52,  94. 

of  worm,  137. 

Blood  vessel.     See  Circulatory  or- 
gans. 

Bluebottle  fly,  80. 
Body  cavity  j  of  starfish,  272. 

of  worm,  136. 
Bone.     See  Skeleton. 
Books  of  reference,  275. 
Brachystola,  52. 
Brain.     See  Nervous  system. 
Branch,  128. 
Branchial  chamber,  of  crawfish,  113 

of  fish,  170. 

of  mussel,  144. 
Budding,  27. 
Bumblebee,  63. 
Butterfly,  36. 

cabbage,  86,  89,  92. 

clover,  36. 

egg,  88,  90. 

larva,  88,  90. 

milkweed,  104. 


NEED.   ZOOL. 20 


305 


306 


INDEX. 


Butterfly,  pupa,  89,  92. 
skipper,  103. 
sulphur,  36. 
swallow-tail,  102. 

Cambarus,  111. 
Cantharidin,  75. 
Carapace,  of  crawfish,  144. 

of  cyclops,  126. 

of  turtle,  199. 
Carolina  locust,  48. 
Catfish,  161. 
Cell,  18. 
Centiped,  109. 
Cephalothorax,  of  crawfish,  114. 

of  cyclops,  127. 

of  spider,  108. 
Chauliognathus,  77. 
Chilopod,  109. 
Chrysemys,  198. 
Cicada,  59. 

Chloragogue  cells,  137. 
Circulation,  demonstration  of,  125, 

163,  179. 

Circulatory  organs,  of  crustaceans, 
119. 

of  fish,  168. 

of  frog,  182. 

of  insects,  52. 

of  mussel,  146. 

of  rabbit,  246. 

of  sparrow,  225. 

of  starfish,  271. 

of  turtle,  201,  202. 

of  worm,  134. 
Class,  128. 

Classification,  101,  127. 
Clitellum,  133. 
Ccelenterata,  22-33. 
Coleoptera,  74,  79. 
Colias.     See  Eurymus. 
Collar  of  snail,  156. 
Collecting  insects,  34. 
Colony,  69. 
Columella,  188.     See  also  Shell  of 

snail. 
Comb,  73. 

Condyle.     See  Skull. 
Conjugation,  17. 
Cranium.     See  Skull. 
Crawfish,  111. 
Cremaster,  89. 
Crustaceans,  111-128. 
Cyanide  bottle,  35. 
Cyclops,  126. 


Development,  of  blister  beetle,  76. 

of  bumblebee,  68. 

of  cabbage  butterfly,  88. 

of  crawfish,  123. 

of  dragon  fly,  47. 

of  fly,  83. 

of  frog,  196. 

of  grasshopper,  55. 

of  mussel,  152. 

of  snail,  157. 

of  spider,  109. 

of  sponge  gemniules,  24. 

of  turtle,  207. 

of  wasp,  71,  73. 

of  worm,  138. 
Diaphragm,  244. 
Differentiation,  25. 
Digestive  organs,  of  crawfish,  121. 

of  fish,  167. 

of  frog,  181.  ' 

of  insect,  53,  94. 

of  mussel,  147. 

of  rabbit,  245. 

of  snake,  210. 

of  sparrow,  223. 

of  starfish,  270. 

of  turtle,  202. 

of  worm,  134. 
Diplax,  42. 
Diptera,  80,  86. 

Directions  for  preparation  of  ma- 
terial for  study,  278. 
Dissosteira,  48. 
Division  of  labor,  32. 
Dorsal  vessel,  52,  94. 
Dragon  fly,  42. 

Ear  sac  of  mussel,  153. 
Earthworm,  130. 
Echinodermata,  266-273. 
Ectoderm,  28. 
Ectosarc,  13,  19. 
Egg  capsules,  of  snail,  160. 

of  worm,  139. 
Egg  sacs,  127. 
Embryology,  158,  160,  196. 
Endoderm,  28. 
Endosarc,  13,  19. 
Endoskeleton,  122,  205. 
Epicauta,  74. 
Epiglottis,  243. 

Esophagus.     See  Digestive  organs. 
Eurymus,  36. 
Eustachian  tube,  180,  242. 
Evolution,  264. 


INDEX. 


307 


Excretory  organs,  of  crawfish,  122. 

of  fish,  169. 

of  frog,  182. 

of  grasshopper,  54. 

of  mussel,  147. 

of  rabbit,  246. 

of  sparrow,  225. 

of  turtle,  202. 

of  worm,  136. 
Exoskeleton,  204,  217. 
Eye,  of  crawfish,  119. 

of  fish,  172. 

of  insects,  39. 

of  snail,  156. 

of  starfish,  269. 

Family,  103. 

Feathers,  218. 

Feeding,  of  amoeba,  14,  15. 

of  bumblebee,  63. 

of  butterfly,  37. 

of  crawfish,  112. 

of  dragon  fly,  43. 

of  earthworm,  130. 

of  fly,  80. 

of  frog,  180. 

of  grasshopper,  49. 

of  hydra,  26. 

of  paramecium,  21. 

of  rabbit,  238. 

of  sparrow,  213. 

of  squash  bug,  58. 

of  starfish,  270. 
Fertilization,  30. 
Fins,  162,  166. 
Fish,  161. 
Foot,  of  frog,  192. 

of  insect,  41. 

of  mussel,  142. 

of  rabbit,  240. 

of  snail,  155. 

of  sparrow,  214. 

of  spider,  108. 

Foramen  magnum.     See  Skull. 
Fresh- water  sponge,  22. 
Frog,  178. 

Gastrula.  159. 
Gemmules,  23,  280,  281. 
Genus,  102. 
Gill,  of  crawfish,  120. 

of  fish,  170. 

of  mussel,  144. 
Glochidia,  152. 
Glottis.    See  Larynx. 


Grasshopper,  48. 
Green  gland,  122. 

Harvest  fly,  59. 

Haunts  and  habits,  of  amoeba,  278 

of  asellus,  125. 

of  back-swimmer,  61. 

of  bee  killer,  85. 

of  beetles,  77-79. 

of  blister  beetle,  74. 

of  bumblebee,  63. 

of  butterfly  (cabbage),  86. 

of  butterfly  (sulphur),  36. 

of  catfish,  161. 

of  centiped,  109. 

of  cicada,  59. 

of  crawfish,  111. 

of  cyclops,  126. 

of  dragon  fly,  42. 

of  earthworm,  131. 

of  fly,  80. 

of  frog,  178. 

of  grasshopper,  48. 

of  hydra,  282. 

of  mussel  (river),  140. 

of  paramecium,  279. 

of  rabbit,  237. 

of  snail  (pond),  154. 

of  sparrow,  212. 

of  spider,  105. 

of  sponge  (fresh- water),  279. 

of  squash  bug,  57. 

of  starfish,  266. 

of  turtle,  198. 

of  wasp  (mud) ,  70. 

of  wasp  (paper),  72. 
Head,  of  blister  beetle,  75. 

of  bumblebee,  64. 

of  butterfly,  39. 

of  dragon  fly,  74. 

of  fish,  162. 

of  fly,  81. 

of  grasshopper,  49. 

of  larva,  90. 

of  pupa,  92. 

of  sparrow,  215. 

of  turtle,  199. 

Heart.     See  Circulatory  organs, 
Hemiptera,  57,  62. 
Hermaphroditism,  30. 
Hinge  ligament,  141. 
Homology,  45,  123. 
Honeybee,  73. 
Hydra,  26,  282. 
Hymenoptera,  63,  74. 


308 


INDEX. 


Hyoid  bone,  185,  222,  243. 
Hypostome,  27. 

Ictalurus,  161. 
Insects,  34-110. 
collecting,  34. 
Intestine.     See  Digestive  organs. 

Kidney.     See  Excretory  organs. 

Labial  palpi  1 

Labru"    '      \SeeMouthparts. 

Lacinia 

Lacteal  system,  250. 

Larva,  08,  88,  90,  96. 

Larynx,  222,  243. 

Lasso  cells,  28. 

Lateral  line,  166. 

Leg  bones,  of  frog,  193. 

of  rabbit,  259. 

of  sparrow,  235. 

of  turtle,  207. 
Legs,  of  bird,  217. 

of  crawfish,  116. 

of  frog,  188. 

of  insect,  40. 

of  rabbit,  240. 

of  turtle,  200. 
Lens.  See  Eye. 
Lepidoptera,  36,  42,  86,  93,  102, 

104,  128. 
Lepus,  237. 

Life  history.    See  Development. 
Life  process,  in  amoeba,  15. 

in  hydra,  30. 

in  insects,  93. 

in  mussel,  150. 

in  sponge,  25. 

in  starfish,  272. 

in  vertebrates,  260. 
Limnea,  154. 
Lizard,  208. 
Locomotion,  in  amceba,  14. 

in  crustaceans,  113,  126. 

in  earthworm,  132. 

in  fish,  162. 

in  hydra,  26. 

in  insects,  97. 

in  mussel,  142. 

in  paramecium,  19. 

in  snail,  156. 

in  sparrow,  214. 

in  starfish,  267. 
Locust,  48.     See  also  Cicada. 


Lucilia,  80. 

Lumbricus,  130. 

Lung.     See  Respiratory  organs. 

Malpighian    tube.      See    Digestive 

organs  of  insect. 
Mammalia,  237-259. 
Mantle,  142,  143,  155. 
Maxilla.    See  Mouth  parts. 
Maxilliped,  117. 

Mesentery,  167,  181,  224,  244,  245. 
Metabolism,  151,  261. 
Metamorphosis,  69,  96. 
Metastoma,  118. 
Mollusca,  140-160. 
Mouth,  of  fish,  165. 

of  frog,  179,  180. 

of  hydra,  28. 

of  mussel,  147. 

of  rabbit,  241. 

of  snail,  156. 

of  snake,  209. 

of  starfish,  268. 

of  turtle,  200. 

of  worm,  139. 
Mouth  parts  of  insects,  39,  44,  49, 

65,  82,  91,  108. 
Mud  dauber,  70. 
Mud  wasp,  70. 
Mucous  membrane,  250. 
Muscles,  of  crawfish,  121. 

of  fish,  174. 

of  frog,  189. 

of  insects,  97. 

of  mussel,  144. 

of  sparrow,  225. 

of  starfish,  270,  271. 

of  turtle,  203. 

of  worm,  136. 
Mussel,  140. 
Myenia,  22. 
Myriapoda,  109,  110. 

Neck,  of  sparrow,  215,  221. 

of  turtle,  200. 
Nephridium  of  worm,  136. 
Nerve  collar,  of  crawfish,  122. 

of  insects,  55. 

of  worm,  136. 
Nervous  system,  of  crawfish,  122. 

of  fish,  170-173. 

of  frog,  185. 

of  insect,  55,  98. 

of  mussel,  147. 

of  rabbit,  250. 


INDEX. 


309 


Nervous  system,  of  sparrow,  235. 

of  starfish,  271. 

of  turtle,  185. 

of  worm,  136. 
Nest,  of  bumblebee,  67. 

of  paper  wasp,  72. 
Nucleus,  15,  18,  20. 
Nutrition,  in  amoeba,  16. 

in  hydra,  30. 

in  insects,  93. 

in  mussel,  150. 

in  vertebrates,  260. 
Nymph,  46,  96. 

Odonata,  42-48. 
Order,  104. 
Organ,  32. 
Orthoptera,  48-57. 
Ovum,  29. 

Palate.     See  Mouth. 

Pallial  line,  149. 

Pancreas.     See  Digestive  organs. 

Paper  wasp,  72. 

Paramecium,  18. 

Passer,  211. 

Pectoral  arch.    See  Shoulder  girdle. 

Pelvic  girdle,  of  fish,  166. 

of  frog,  193. 

of  rabbit,  258. 

of  sparrow,  234. 

of  turtle,  207. 

Pericardium.     See  Circulatory  or- 
gans. 

Peristome,  20. 
Pharynx,  165,  242. 
Piscus,  161,  178. 
Plastron,  204. 
Plumage,  218. 

Proboscis.    See  Mouth  parts. 
Pronephros,  169. 
Protozoa,  12,  21. 
Pseudemys,  198. 

Rabbit,  237. 

Radius.    See  Arm  bones. 

Radula,  157. 

Rana,  178. 

Reagents,  276. 

Reproduction,  in  amoeba,  17. 

in  hydra,  31. 

in  insects,  96. 

in  starfish,  273. 

in  vertebrates,  262. 

vegetative,  27. 


Reproductive  organs,  of  crawfish, 
121. 

of  fish,  167. 

of  frog,  182. 

of  grasshopper,  53. 

of  hydra,  27,  29. 

of  mussel,  148. 

of  starfish,  269. 

of  turtle,  202. 

of  worm,  135. 
Reptilia,  198-211. 
Respiration,  in  amoeba,  16. 

in  cyclops,  127. 
Respiratory  organs,  of  crawfish,  116. 

of  fish,  170. 

of  grasshopper,  53. 

of  insects,  94. 

of  mussel,  151. 

of  rabbit,  249. 

of  snail,  156. 

of  snake,  210. 

of  sparrow,  222,  224. 

of  spider,  108. 

of  turtle,  203. 
Rib,  176,  205,  231,  254. 
Robber  fly,  85. 
Rostrum,  of  bugs,  58. 

of  crawfish,  114. 

Scapula.     See  Shoulder  girdle. 

Schistocera,  52. 

Segmental  organ.    See  Nephridium 

of  worm. 

Segmentation,   of    arthropods,  39, 
113,  133,  134. 

of  oosperm,  158,  196. 
Sensation,  in  amoeba,  18. 

in  hydra,  32. 

in  insect,  98. 

in  mussel,  153. 

in  vertebrates,  263. 
Serial  homology,  123. 
Setae,  132. 
Shell,  of  mussel,  148. 

of  snail,  155. 

of  turtle,  203. 
Shoulder  girdle,  of  fish,  166. 

of  frog,  192. 

of  rabbit,  257. 

of  sparrow,  233. 

of  turtle,  206. 
Siphon,  144. 
Skeleton,  of  crawfish,  114,  122. 

of  fish,  175. 

of  frog,  191. 


310 


INDEX. 


Skeleton,  of  insect,  38. 

of  rabbit,  253. 

of  sparrow,  227. 

of  turtle,  203. 
Skin,  of  fish,  161. 

of  frog,  190. 

of  insect,  38,  92. 

of  rabbit,  239. 

of  sparrow,  217. 

of  turtle,  204. 

of  worm,  136. 
Skull,  of  fish,  171. 

of  frog,  194. 

of  rabbit,  255. 

of  sparrow,  227. 
Snail,  154. 
Snake,  208. 
Sparrow,  211. 
Specialization,  21,  33. 
Species,  102. 
Sperms,  29,  137. 
Spicules,  23,  280. 
Spider,  105. 
Spinal  column,  of  fish,  169. 

of  frog,  191. 

of  rabbit,  253. 

of  sparrow,  230. 

of  turtle,  205. 

Spinal  cord.    See  Nervous  system. 
Spiracle  of  insect,  42,  51. 
Spleen,  168,  182,  224,  24(5. 
Sponge,  22. 

gemmules,  23,  280,  281 
Squash  bug,  57. 
Starfish,  266. 
Sternum,  of  frog,  192. 

of  rabbit,  254. 

of  sparrow,  232. 

Stomach.     See  Digestive  organs. 
Stylets,  125. 
Swimmer,  115. 
Syrinx,  222. 


Tarsus.    See  Foot. 
Teasing,  283. 
Teeth.     See  Mouth. 
Telson,  114. 

Test  of  strength  of  beetle,  79. 
Tetraopes,  78. 
Thoracic  duct,  250. 
Thorax,  of  insects,  40. 

of  rabbit,  243. 
Thousand-legs,  110. 
Thymus,  250. 
Tissue,  32. 

Tongue.     See  Mouth. 
Trachea.     See  Respiratory  organs 
Tracheal  gills,  47,  94. 
Tracheal  tube,  53,  94. 
Turtle,  198. 

Ulna.    See  Arm  bones. 
Umbo,  141. 
Unio,  140. 

Uterus,  262. 

Vacuole  (vesicle?),  15,  20 
Vegetative  reproduction,  27. 
Veins,  of  fish,  163,  168. 

of  frog,  183. 

of  mussel,  146. 

of  rabbit,  246. 

of  sparrow,  226. 

of  turtle,  202. 

Vermiform  appendage,  246. 
Vertebra.     See  Spinal  column. 
Voluntary  motion,  in  amoeba,  17. 

in  hydra,  31. 

in  insect,  97. 

in  mussel,  152. 

in  vertebrates,  262. 

Water- vascular  system,  270. 
Wing,  213,  216. 
Wing  bones,  233. 
Worm,  130. 


36075 


M577041 


QL42 
N4 

Educ 
Lib. 


